Sarah Thomas - Round-Trip Angel Island

Clockwise loop around Angel Island from Aquatic Park

16.1 km (10.0 miles)

6 hours, 9 minutes on 26 June 2019

Observed and documented by Evan Morrison


  • Name: Sarah Thomas
  • Gender: female
  • Age on swim date: 37
  • Nationality: United States
  • Resides: Conifer, Colorado

Support Personnel

  • Brent McLain - pilot
  • Robin Rasmussen Rose - crew
  • Evan Morrison - observer / documentation

Escort Vessel: Tango (San Francisco / Hyde St Marina)

Swim Parameters

  • Category: Solo, nonstop, unassisted.
  • Rules: MSF Rules of Marathon Swimming, without exception or modification.
  • Equipment used: Swimsuit, silicone cap, goggles.

Route Definition

Start @ SERC/Dolphin beach in Aquatic Park, exit through Aquatic Park opening, clockwise around Angel Island, return to SERC/Dolphin beach via Aquatic Park opening.

  • Body of Water: San Francisco Bay
  • Route Type: island loop
  • Start & Finish Location: Beach between SERC & Dolphin Club docks, Aquatic Park, San Francisco (37.808145, -122.421402)
  • Minimum Route Distance: 16.1 km (10.0 miles)


LongSwimsDB: Round-Trip Angel Island

Swim Data

  • Start: 26 June 2019, 04:09:49 (America/Los_Angeles, UTC-7).
  • Finish: 26 June 2019, 09:19:54
  • Elapsed: 6 hours, 9 minutes, 5 seconds.

Summary of Conditions

Feature Min Max
Water Temp (F) 60 62
Air Temp (F) 56 60
Wind (Beaufort) 0 5

GPS Track

Trackpoint frequency: 10 minutes. Download raw data (CSV).

Speed Plot

Nutrition: Carbo Pro flavored with apple juice. First feed at 1 hour, then every subsequent half-hour.

Observer Report

by Evan Morrison

On the morning of Wednesday, June 26, 2019, Sarah Thomas completed an unassisted solo swim of the “Round-Trip Angel Island” route in San Francisco Bay. Sarah swam the 16 km clockwise loop around Angel Island from Aquatic Park in 6 hours, 9 minutes, 5 seconds - about a minute faster than Cathy Delneo’s women’s course record from 2013, despite marginal weather conditions.

Sarah experienced prototypical early-summer San Francisco conditions: water temp from 60-62, air temp from 56-60, and winds ranging from Force 4 on the outbound channel crossings, Force 4-5 on the inbound channel crossings, and glassy Force 0 on the north and east shores of Angel Island. She swam incredibly consistently - I never recorded a tempo slower than 66 strokes per minute, or faster than 68.

Sarah was the 16th person to swim the RTAI (one of the MSF Toughest Thirteen) since 1984. Capt. Brent McLain of SF Boat Support piloted the swim, Robin Rasmussen Rose served as crew, and I documented. Sarah fed directly from the boat, without a kayak escort.

A few months previous, I had identified June 24-27 as offering a favorable tidal window for a RTAI attempt. Sarah consulted her work schedule, and we settled on a somewhat risky single-day window: Sarah would fly from Denver the evening of June 25, swim the morning of June 26, and fly home that same evening.

Predicted surface currents, San Francisco, Golden Gate:
2345 2.3E 0425 slack 0559 0.7F 0813 slack 1151 1.8E

Spring and early summer in SF are frequently windy - but if it was swimmable, she would swim. Given Sarah’s busy season ahead (including an unprecedented four-way English Channel attempt), there was little leeway to reschedule.

When we met at 3:30am on June 26, it was already blowing 10 knots, gusting to 15. A local swimmer likely would have postponed to wait for better weather. But Sarah was here now - not tomorrow, not next week. So she swam.

We met Capt. Brent at Hyde Street marina and loaded up Tango, his 27’ RHIB. We motored around the corner into Aquatic Park cove, idling a few yards offshore while Sarah applied grease and sunscreen. After swimming into the beach between SERC and the Dolphin Club, she cleared the water and re-entered to begin the swim at 4:09:49.

Outbound: Aquatic Park to Point Campbell

  • 04:09:49. Start @ SERC/DC beach.
  • 04:21. Opening.
  • 05:18. Abeam Alcatraz lighthouse.
  • 06:26. Pt Knox.
  • 06:36. Pt Stuart (Raccoon Strait).
  • 06:56. Pt Lone (Ayala Cove).
  • 07:14. Pt Campbell (top of island)

On the outbound leg, Aquatic Park to Angel Island, Sarah’s progress was slowed considerably by Force 4 west winds. We were delayed an additional 5 minutes by inbound tanker vessel Matsonia. Brent briefly navigated due west (parallel to shore), and Sarah was startled as the hulking ship passed by just 50 yards or so in front of us.

Vessel Matsonia, 6:26am

All considered it took 1hr 8min to reach Alcatraz, and 2hr 26min to reach Pt. Stuart and the Raccoon Strait. I’m sure Sarah sensed the marginal conditions and slow progress, yet she betrayed little emotion. She fed quickly on the half-hour, with few words, and resumed her metronomic 67-stroke tempo.

The water smoothed out considerably as we approached Angel Island, thanks to the Marin Headlands’ protection from the westerlies. There was little flood current left in the Raccoon Strait by this time, but the glassed-off and surprisingly warm (62F) water offered a welcome respite to enjoy postcard views of downtown Tiburon.

We were about half an hour behind schedule when she reached Pt. Campbell, the top of Angel Island and the route’s geographic halfway mark.

Inbound: Point Campbell to Aquatic Park

  • 07:14. Pt Campbell
  • 07:27. Pt Simpton.
  • 07:45. Quarry Pt.
  • 08:07. Pt Blunt.
  • 09:35. Alcatraz east end.
  • 10:12. Aquatic Park Opening.
  • 10:20. Finish @ SERC/DC beach.

From Pt. Campbell it was another 53 minutes through smooth, slack water to Pt. Blunt, along the gorgeous east shore of Angel Island, past the historical immigration station at China Cove and the East Garrison barracks at Quarry Point.

Approaching Pt. Blunt, the SE corner of Angel Island, we could see the wind before we could feel it. The strong westerlies from earlier hadn’t actually decreased - we had just been protected by the lee of well-placed land masses. That protection would soon end.

Just after 8am we inched past Blunt Rock into the white-capped north shipping channel. Sarah was utterly unfazed by this development. If anything she kicked it up a notch - 67-68 stroke tempo, powering through the chop. She crossed the north shipping channel in 1hr 28 min. All the while we nervously anticipated currents threatening to push us off course - but they never came.

After a brief respite in the lee of Alcatraz, we entered the south shipping channel, navigating straight on the Aquatic Park opening. The wind was now a solid Force 5, but Sarah appeared gleeful as she stroked through the crashing waves.

The only flaw in an otherwise picture-perfect track came at the very end, when the long-awaited ebb pushed Sarah a few yards west of the Opening, costing her a couple minutes of swimming along Muni Pier. Brent followed Sarah into the cove, cautiously, and edged up to the dock as Sarah finished - a few seconds before 9:20am.

Photo by John Grunstad

Of the six RT Angel Island swims I’ve participated in (5 observing and 1 swimming; 5 successful and 1 DNF), each one has been a memorable experience, each with distinct joys and challenges. This one I’ll remember for the sheer thrill of watching a world-class swimmer take on my favorite local route - one I’ve helped develop and promote. The swim was also notable for hewing surprisingly close to plan, despite sustained heavy conditions. In the end, Sarah finished less than 10 minutes off my timeline for a 6-hour swim.

It helped that we had a very forgiving tide - 0.7 knots of flood going into 1.8 knots of ebb. In retrospect, and given the early winds, we could have splashed 30-45 minutes earlier; but that’s counterbalanced by 30-45 minutes less sleep on an already very early morning. And it helped to have a swimmer with excellent speed and otherworldly consistency of pace.

Lucky or good? It’s a false choice. On the Round-Trip Angel Island, it’s best to be lucky and good!


Sarah Thomas - Round-Trip Angel Island from MSF on Vimeo.

Weather Data

Via NOAA Station FTPC1 - Fort Point, San Francisco, CA

Water Temperature


Air Temperature


Wind Speed

(gust = dotted line)