Ken Mignosa - Dumbarton Rail Bridge to Anita Rock

Dumbarton Rail Bridge to Anita Rock

49 km (30.4 miles)

21 hours, 17 minutes on 26-27 May 2019

Observed and documented by Kelley Prebil and Cathy Harrington

Longest duration swim in San Francisco Bay (continuous, unassisted)



  • Name: Ken Mignosa
  • Gender: male
  • Age on swim date: 55
  • Nationality: United States
  • Resides: Santa Clara, California

Support Personnel

  • John Sims - pilot
  • Tom Wilhelm - pilot
  • Robin Rasmussen Rose - crew chief
  • Stephanie Duhau - SUP, crew
  • Miguel Melendez - kayaker, photographer
  • Kelley Prebil - observer
  • Cathy Harrington - observer

Escort Vessel: Kristine Ann (Oyster Point)

Swim Parameters

  • Category: Solo, nonstop, unassisted.
  • Rules: MSF Rules of Marathon Swimming, with exception of Suunto GPS watch worn by swimmer.
  • Equipment used: textile brief, silicone cap, goggles, GPS watch

Route Definition

Route Notes

Original route plan was Dumbarton Rail Bridge to Golden Gate Bridge (“5 Bridges”).

The swim ended just offshore from Crissy Field, due to adverse currents. To define a repeatable, measurable route, we used Anita Rock - the nearest permanent, above-water feature that Ken swam beyond.

Additionally, for the route portion between the Dumbarton Rail Bridge to the San Mateo Bridge, we used the narrow navigation channel rather than strictest, shortest line between these two landmarks. This part of San Francisco Bay is unnavigably shallow, apart from the channel.

Route Waypoints

Latitude Longitude Landmark
37.497333 -122.110076 Dumbarton Rail Bridge
37.518713 -122.140675  
37.552743 -122.190456  
37.583494 -122.250881 San Mateo Bridge
37.633198 -122.298088  
37.791744 -122.384691 Bay Bridge
37.807953 -122.400355 Pier 29
37.811784 -122.408638 Pier 39 breakwater
37.812327 -122.419839 Hyde Street breakwater
37.808334 -122.453557 Anita Rock


No known previous swims of this route. The only known longer (by distance) San Francisco Bay swim is Dave Kenyon’s swim from the Carquinez Bridge to Oyster Point - 56 km (34.8 miles) in 9 hours, 35 minutes on August 22, 1984.

Swim Data

  • Start: 26 May 2019, 15:21:58 (America/Los_Angeles, UTC-7).
  • Finish: 27 May 2019, 12:39:40
  • Elapsed: 21 hours, 17 minutes, 42 seconds.

Summary of Conditions

Feature Min Max
Water Temp (F) 63 66
Air Temp (F) 57 64
Wind (knots) 1-2 15

GPS Track

Trackpoint frequency: 30 minutes. Download raw data (CSV).

Speed Plot

Nutrition: Carbo Pro + water, alternating with GU every 30 min after first hour.

Observer Log

Download PDF


Every Breath You Take - Five Bridges Swim Attempt

by Ken Mignosa

For many years, even before I joined the South End Rowing Club, I joked about doing a swim from south San Francisco Bay to the Golden Gate. And for many years, it was just that: a joke. I never imagined such a swim was really possible at all much less that I’d be the one to attempt it. I was wrong on both counts.

In the fall of 2018, after increasing long swim adventures over the prior 2 years, I had begun to believe that perhaps I could turn my joke into a reality, and I began planning a swim that I then thought of as “Four Bridges”. The swim would go from the Dumbarton Bridge near Redwood City to the Golden Gate, and it would be distance of 30+ miles. Along the way to the Golden Gate Bridge, I’d pass by the San Mateo Bridge and Bay Bridge.

Late in the planning stages of the swim, in fact, it was only a week or so before the swim, it became “Five Bridges”. There’s a rail bridge less than a mile south of the Dumbarton Bridge, and that is where the swim started. The swim had been planned with the help of John Sims and Les Mangold to take advantage of currents in the bay. In general, the idea was to find a weekend when the ebb tides were both stronger and longer than the flood tides. That ended up being Saturday of Memorial Day weekend in 2019.

On Friday afternoon, it became clear that the Saturday swim plan was not going to work. 20+ knot winds descended on San Francisco on Saturday evening, and they were going to last through the night well into the next day. That much wind would make the swim dangerous for both the swimmer and crew. However, by Sunday evening of the same weekend, the winds were supposed to die down by the late PM hours and stay mild into Monday afternoon.

A change by a day was an iffy affair. Would it be possible to reschedule the crew and boats on such short notice? By some miracle it was! I was happy that the swim was going to go on, and with the same crew I had chosen in the first place. It was an up-side to doing a swim close to home on a holiday weekend.

Most of the lengthy swims I had done prior to this were away from home, and my family supported me as I trained and got ready for the swims. However, it was rare for my wife to be able to join me as I loaded up a car (or packed for a flight), took gear to a boat, and headed off on a swim. While Tammy was not going to accompany me on the swim, it was a treat that she was able, and willing, to help prep gear, load up a car, drive me to the Oyster Point Marina, load up the boat, and later unload when she picked me up after the swim. Another up-side of doing a swim close to home on a holiday weekend.

Sunday mid-day the crew, Tammy and I gathered at John Sims’ boat, the Kristine Ann. We loaded gear and food onto the boat, and after that Tammy went home. John provided his safety briefing, and then the Marathon Swim Federation (MSF) observers, Cathy Harrington and Kelley Prebil, provided a reading of the rules that would guide the swim.

In addition to John and the observers, the crew consisted of Robin Rose as crew chief, and Miguel Melendez as photographer and kayaker. Ironically, the kayak was never used during the swim due to the wind. Tom Wilhelm was RIB pilot and boat co-pilot. Greg Gubser was originally scheduled to co-pilot the boat, but the one day schedule change did not work for him. Nevertheless, as the harbor master at Oyster Point, Greg both saw us off when we headed out on Sunday, and welcomed us back when we returned on Monday.

With crew aboard and gear stowed we left Dock 11 at Oyster Point, and headed down to the Dumbarton Rail Bridge. The journey south was exceptionally windy and rough. I wasn’t worried that the RIB being towed off the stern of Kristine Ann was madly bobbing around in the serious wind waves and white caps because I “knew” the wind was going to die down later that night.

As we passed the San Mateo Bridge and headed further south, the wind died down somewhat, and it started to rain, and jokes abounded about calling the swim on account of the rain. When we arrived at the Dumbarton Rail Bridge at about 3:00 on Sunday afternoon the rain had slowed, but it was still pretty windy. As I was getting ready to get in the water for what was expected to be about a 20 hour swim I was unconcerned about the wind because I “knew” the wind was going to die down later that night.

The wind might have stopped the swim for some people. However, I have been incredibly lucky to be a member of the South End Rowing Club, and much of my training has happened off the shores of the Mighty South End in and around San Francisco Bay. As a result, I had swum for many hours in strong winds, big swells, and against strong tides in the same bay where my Five Bridges swim was taking place. I thought that swimming in nasty wind for a few hours, until the wind died down later that evening, would be fine because I had quite a bit of experience with windy condition in the bay.

I got in the water a few minutes before 3:30PM on Sunday, 26 May, 2019, and began my swim, and a windy swim for a few hours was indeed fine. It was not beyond conditions in which I had trained. Swimming in windy conditions can be difficult because all the wind waves that seem so inconsequential from the shore or from a boat can make it hard for a swimmer to breathe. The swim stroke must altered to lift the head a little further out of the water when breathing to make breathing possible without swallowing water, but not so far as to make the swim stroke inefficient.

The other issue that comes up in bumpy water is stabilization. Legs have to do double duty when conditions are rough. Legs provide propulsion and stabilization at the same time, and this can be tough on the leg muscles. Somewhere around the 10 hour mark my legs muscles started to spasm and cramp. The muscle pain only came during feeds when I changed from horizontal to vertical, and attempted an egg-beater kick while taking feeds. The pain in aductors, quads and hamstrings was excruciating. The aductor spasms were the worst. I could see and feel the “knots” in the muscles moving on my leg as I felt the screaming pain, and tried to remain calm. Thankfully, the muscle spasms weren’t a problem while swimming. So I did my best to make the feeds quick, and get back to swimming as soon as possible.

I swam in the windy afternoon into the evening unfazed. I had probably been fighting for every one of my breaths during the swim for several hours, but I was unconcerned about the wind as night fell because I “knew” the wind be die down soon.

The wind did not die down soon. The wind did not die down later that night, the wind did not die down into Sunday morning. A lovely sunrise was accompanied by strong wind. By the time the sun rose, I had been fighting for every breath I took for over 14 hours. Now I was in a realm that exceeded my training. I was alternately tired of having to fight with the wind, and angry that I had been betrayed by the forecast at windguru (a wind forecasting website favored by swimmers, sailors, surfers, etc.) . As the hours wore on in the late morning, I wondered if the wind was ever going to die down, and I wondered if I’d be able to complete the swim as I grew more tired and sore.

A bit south of Hunters Point, nearly 16 hours into my swim, the wind died down. Finally!

My swim plan called for starting the swim against a weak flood tide at the Dumbarton Rail Bridge, continuing on north to the Dumbarton Bridge and then the San Mateo Bridge. Somewhere not far from the San Mateo Bridge the tide was to change to an ebb effectively helping me on my journey north. Later, there would be one more flood to swim against. I would have to arrive somewhere around Hunters Point no later than 8:30AM to take advantage of a final ebb tide, and that strong ebb would speed me on my way to the Golden Gate.

Here I was, despite many hours of plodding through strong winds and stronger than expected floods, and weaker than expected ebbs, near Hunters Point at close to the right time! And the wind had finally died down! Hurray!! I was pleased because I “knew” that the wind was supposed to remain mild for the rest of my swim, and I now had the tide to assist in completing the swim.

For about a half hour I enjoyed the calm conditions. I lengthened out my stroke. I reveled in not having to fight for every breath I took. I relaxed. I had calm conditions and tide to help me finish the swim! Except the ebb hadn’t really started yet, and then the wind picked up again.

I still had a fair distance to go before reaching the Bay Bridge and a 10K to complete between the Bay Bridge and the Golden Gate after that. Before we passed the Bay Bridge, I thought about how much food I had brought, and the fact that the swim was now behind schedule due to the late arrival of the ebb. Would my food hold out, did the boat pilots and crew have time to stay with the swim longer? I was pretty wiped out from fighting for air for many hours, and now I was facing the prospect of continuing to fight for every breath I took all the way to the Golden Gate. I seriously considered ending the swim at the Bay Bridge.

I asked my crew chief, Robin Rose, to take stock of the feeds left available to me. She said there was enough and urged me on as did the rest of the crew. When we crossed under the Bay Bridge, there was a pause for photos and camaraderie. The crew on the boat was urging me on, but I knew I had barely enough food to complete a swim and only about 2 and a half hours before the ebb tide ended. On my best days, I cannot complete a 10K in 2 and a half hours or less, and that was what lay ahead. And the wind was picking up force.

Under the support and urging of my crew, I continued on. We flew past the Ferry Building in San Francisco, past piers 7, 11, 15, 23, 39 (yes there were more, but I don’t know them all by sight as I do these) pushed on by the expected strong ebb. We continued speeding along as we approached Alcatraz. By then the wind was howling and there were large swells and wind waves. In what might have been my last feed before pushing on to the Golden Gate it was impossible to transfer feeds because conditions were too rough. Even if the feed had somehow gotten to me, it was too rough for me to eat or drink anything without getting mouthfuls of bay water along with the food. By then feeding was the least of my concerns. Certainly I was tired, sore and hungry, but in those windy conditions I was having a harder time breathing than I had had during the rest of the swim. In no more than half of my breathing attempts was I able to get air. Instead I gobbled up what felt like half the bay, or I got slapped with wind waves, and had the bay water shoved down my throat and lungs. From Alcatraz onward, I had to stop every few strokes to cough up the bay water and get a few breaths before continuing on.

Despite my extreme discomfort, we still made good progress because of the ebb tide. We went on past Aquatic Park, past Fort Mason, past the Palace of Fine Arts and onto Crissy Field. And there we hit a wall, figuratively.

The flood had come early, and it was strong, over 3 knots. At my best I can sprint for awhile at about 3.5 knots. However, that assumes I can breathe and take nutrition somewhere along the way. Neither regular breathing nor feeding were going to happen under these windy conditions.

I had noticed an increasing number of sailboats as we approached the Golden Gate,. The sailors were loving the high winds, and there were lots of them because it was a holiday weekend. A swimmer in the midst of excited sailors was hard to keep safe. Unbeknown to me, by crew fought tirelessly to keep the sailboats from running me over. My RIB escort, Tom Wilhelm, was circling around me warning sailors off, the boat pilot was hailing people over loudspeaker, and radioing those he could, and the crew was waving warning flags. I later learned that some of the sailors were pretty belligerent about staying clear of the swim. I guess I was in their way.

I had made a backup plan for my swim in case our timing was poor and there was a flood as I approached the Golden Gate. I knew from my experiences swimming out of the South End Rowing Club that if I swam close along the shore the tide would be weaker there, and I should be able to make it to the bridge. This would have the side benefit of getting me clear of the sailors. Sadly, on this day, the tide was not much weaker in the shallow waters close to shore, and the wind was still making it hard to breathe though it was a little weaker.

The swim had now exceeded 20 hours. I headed toward shore, and I tried sprinting for about 20 meters, and found I could make slow progress toward my goal. I was also aware that along the way I’d be hungry, but any stop for feeds would cause me to lose hundreds of meters I’d worked so hard to gain, and I’d be fighting for every breath I took. I knew this wasn’t going to be a successful strategy, and I told the observer, Kelley Prebil, that I wanted to call off the swim there.

As I was getting out of the water onto the Kristine Ann, I had no regrets. My goal with this swim was partly to live out something that had started as a joke, but mostly as a training swim for a much longer swim I have planned for later in 2019. I absolutely got excellent training out of the swim. Among other things, I learned that even if you have to fight for every breath you take, you can still keep on swimming…for many, many hours.

After the swim was complete, my crew chief, Robin Rose, contacted the co-founder of MSF, Evan Morrison. She inquired if the swim could be at least somewhat officially recognized. As a result of her inquiries and the work of Kelley Prebil, Cathy Harrington and Evan Morrison, the swim will be recognized as Dumbarton Rail Bridge to Anita Rock. The swim is probably the longest swim ever done in San Francisco Bay in both distance and time.

The final tally for distance and time was over 52 kilometers in over 21 hours. The officially recognized swim will be the shortest route distance between the Dumbarton Rail Bridge and Anita Rock which is about 47.8 kilometers.


Click to enlarge.