Visualizing the tides of San Francisco Bay

Visualizing the tides of San Francisco Bay

Just for fun, here is every high and low tide for San Francisco Bay in 2016. Red dots are the high tides; blue dots are the low tides. (click to enlarge)

sf high and low tides
data source

I found it interesting that the highest low tide of the year is lower than the lowest high tide of the year. There’s a certain narrow range of water levels — about 3.1-3.4 feet — which sees neither high tides nor low tides. Perhaps there’s some obvious reason for this, known to oceanographers, but it was news to me! I’m also curious if the non-overlap of high and low tides is true everywhere?

Any tide gurus out there?…


Swim Report: Candlestick Point to Aquatic Park

Swim Report: Candlestick Point to Aquatic Park

The following events took place in May 2015; clearly I’m faster at swimming than writing.

Candlestick to Aquatic Park is the longest swim offered on the South End Rowing Club‘s calendar, coming in just a hair under 10 miles by the shortest swimmable route. Due to the current assist, it swims more like a 10K for faster swimmers, or ~8K for slower swimmers.

(Assistive currents benefit slower swimmers more than faster swimmers — consider the relatively narrow range of finish times for, e.g., the Manhattan Island Marathon Swim, compared to, e.g., an English Channel swim).

I’ve written about this swim before, from the perspective of a support kayaker.

After a several months-long period of swim-shiftlessness, I scrawled my name on the sign-up sheet, inspiring a two-week burst of training. Proving once again that nothing happens without goals!

Anyway, the Candlestick Swim.

5-minute intervals
5 minutes per trackpoint

Starting from a sandy beach in front of the old stadium site (as I recall, this swim took place in the midst of the demolition), you enter the water gingerly, hoping not to disturb the biohazardous sludge on the bottom.…


2nd Annual MSF Photo Calendar

2nd Annual MSF Photo Calendar

Once again MSF are pleased to offer a Marathon Swimming Photo Calendar. Last year’s inaugural edition was a global hit, hung on walls in every continent except Antarctica (yes, there’s a post office in Antarctica). Donal and I are grateful to everyone who submitted images this year, and will be sending a complimentary calendar to the selected photographers.

Buy your 2016 MSF Photo Calendar here (while supplies last).

If you are a marathon swimmer, or have a marathon swimmer in your life, or have someone in your life who appreciates marathon swimmers, or have someone in your life who should appreciate marathon swimmers, these images will provide inspiration through the coming year.

They also make a great training log:

training log

A preview:

$20 USD per calendar, inclusive of shipping, handling, and sales tax. Discounts available for multi-calendar purchases.

Oh, and we’re pleased to offer properly-localized week formats this year — Sunday through Saturday for calendars shipped to North America, and Monday through Sunday for everywhere else.

Once again:

Round Trip Angel Island: Observer Log

Round Trip Angel Island: Observer Log

Report by Cathy Delneo on my Round-Trip Angel Island swim this past Sunday. Cathy is a Manhattan Island soloist, an IISA Ice Miler, a member of the first women’s Farallon Island relay, and the 5th person (and first woman) to complete a solo Round-Trip Angel Island.

Round Trip Angel Island Swim

Sunday, July 12, 2015

Swimmer: Evan Morrison

Pilot: Paul Saab

Observer: Cathy Delneo

Boat: South End Rowing Club inflatable Miller Time (a.k.a. “Big Red”)

Course: South End Rowing Club beach, San Francisco past the west end of Alcatraz Island, toward the west end of Angel Island, into Raccoon Straits on the north side of Angel Island, then back to San Francisco on the east sides of Angel Island and Alcatraz Island, finishing on the SERC beach.

Rules: MSF Standard

Jump: 4:49 am


We were aware that 3 vessels were scheduled to come through the Golden Gate, with the first scheduled to be in the incoming channel (between Alcatraz and SF city front) around 5:30 am. This led to a slightly earlier jump than planned.

4:49 am – Swimmer walked into smooth and calm water at the SERC beach

5:08 am – 64 strokes per minute

5:20 am – 1st feed, about ½ green bottle

Swimmer breathes right, so pilot positioned boat on the swimmer’s right.…


Round-Trip Angel Island: A Devil of a Swim

Round-Trip Angel Island: A Devil of a Swim

If I had to nominate a single, definitive marathon swim of San Francisco Bay, it would be the Round-Trip Angel Island.

Start at Aquatic Park’s “swimmers’ beach” between the South End and Dolphin clubs, swim out into the Bay, past Alcatraz to Angel Island (3.5 miles), around the island (3 miles), and then back to Aquatic Park (3.5 miles). Ten “honest” miles by shortest route, mostly perpendicular to the tidal flow.

Round-Trip Angel Island route
Round-Trip Angel Island route

Angel Island is the second largest island inside the Bay (behind Alameda), and has functioned at various times through history as a military fort, an immigration station (like a west coast Ellis Island), and currently as a California State Park.

angel island
Angel Island from the air. Yerba Buena and Treasure Islands, Bay Bridge, San Francisco city skyline, and Alcatraz visible in background.

The Round-Trip Angel Island (RTAI) is like the Round-Trip Alcatraz (RTA)…squared — almost literally, by distance. The 3.2-mile Round-Trip Alcatraz is an annual South End club swim — and Water World Swim organizes a popular public version called the “Swim Around the Rock.” A RTAI swim involves many of the same features and challenges as a RTA: scenic views, iconic landmarks, complicated currents, and busy shipping channels — requiring skill from both the pilot and swimmer.…


Standardized Swims and Routes

Standardized Swims and Routes

As previously defined, a swim route is a predetermined, abstract path between a start location and a finish location, composed of a straight line or series of connected straight-line segments.

Let’s further define a standard swim route as an established, recognized route used by most (or all) attempts of a given swim. A standard route is established either informally, through a history of successful swims along the route; or formally, by a sanctioning organization.

Finally, let’s define a standardized swim as a swim for which a standard route has been established.

Most well-known marathon swims are standardized swims, with standard routes:

  • An English Channel swim, by default, covers the straight-line route between Dover and Cap Gris Nez.
  • A Catalina Channel swim, by default, covers the straight-line route between Doctor’s Cove/Arrow Point and Point Vicente.
  • A Boston Light Swim starts at Little Brewster Island and finishes at the L Street Bathhouse, via a meandering route among several islands in Boston Harbor.

Why does this matter? Consider the following hypothetical:

Perhaps I’m not satisfied with the typical English Channel route — I want to be different and special and do something no one’s ever done before. …


Measuring Non-Straight-Line Swim Routes

Measuring Non-Straight-Line Swim Routes

In the previous article, I discussed the difference between a swim route and a swim track, and how the measured distance of a marathon swim is always the length of the route, not the length of the GPS track. To demonstrate this principle I contrasted the standard English Channel route (a 20.5 statute mile line between Dover and Cap Gris Nez) and a typical English Channel track (a swooping S-curve as the swimmer is pushed back and forth by the tides).

Aha!, you might say: Not every swim route is a straight line! What about an island circumnavigation? Or a swim down a curving river?

Let’s review the definition of “swim route” from the previous article (emphasis added):

A swim route is a predetermined, abstract path between the start and finish, composed of either a straight line or (if the straight-line path is interrupted by another land-mass) a series of connected straight-line segments.

So, by this definition, even a non-straight-line route can be understood as a “series of connected straight-line segments.” The key in measuring a non-straight-line route is knowing how to select the intermediate waypoints — the “nodes” connecting each line segment.…