The warmest winter on record in San Francisco Bay

The warmest winter on record in San Francisco Bay

Here in San Francisco, the common sauna wisdom is that we just experienced one of the warmest winters in recent memory. The Dolphin Club’s Polar Bear Challenge was hardly challenging, and the South End’s “Dreaded 9th” of February swim was hardly dreaded.

Just how warm was it, though? I crunched the numbers from the NDBC, because, well, why not.

Here we see the last 15+ months of data from the Crissy Field station (FTPC1) inside San Francisco Bay, plotted in solid black. The dashed green, red, and blue lines show the long-term average, maxima, and minima for each day of the year, summarized over the eight years of available data from that station.

san francisco bay water temp

From July 2014 until just the past few days (early April 2015), Bay waters have been hovering 2-3 degrees (F) above the all-time highs (going back to 2006), and about 5 degrees above the long-term averages.

Eight years isn’t much data, unfortunately. Can we do better?

A bit: Lightstation 46026 – about two-thirds of the way out to the Farallones – has data going back to 1982.…


Information Wants to be Free: Sandettie Lightship and the English Channel

Information Wants to be Free: Sandettie Lightship and the English Channel

(tl; dr — 10 years of English Channel weather data, in a single CSV file. And some fun charts.)

Weather can turn on a dime in the English Channel, and the dreams (and finances) of English Channel swimmers often turn on the weather.

sandettie lightship
Location of Sandettie Lightship in the English Channel

The most important source of information about that weather is a 156-foot lightvessel called Sandettie, which serves as both a floating lighthouse and a weather station. Here’s a nice photo.

Sandettie collects a variety of important meteorological data – air and sea temperatures, wind speed and direction, wave height and period, humidity, and barometric pressure. These data are then fed back to the UK Met Office, who publish the most recent 24 hours’ of observations on their website.

Anything before the last 24 hours are what the Met Office call “chargeable data” — at the rate of £6800 per 10 years, per two elements (e.g., air temp & sea temp). According to the today’s exchange rate, that converts to no less than $11,575 USD.

LOL! (And yes, I actually requested a quote from the Met Office.)

Just sayin': In the US, quality-controlled meteorological data are available from NOAA’s National Data Buoy Center — for free.


Most popular threads in the history of the Marathon Swimmers Forum

Most popular threads in the history of the Marathon Swimmers Forum

Since launching in March 2012, the Marathon Swimmers Forum has grown to 935 verified members who have contributed 13,195 comments in 796 discussion threads.

Of those 796 threads, the most popular by far (as measured by page-views) was the discussion of Diana Nyad’s purported swim from Cuba to Florida in September 2013.

The top 25 threads in the history of the Forum are as follows. Relative page views for each thread are shown (indexed to the Nyad thread = 100).

  1. 110 miles, 53 hours: Questions for Diana Nyad [100]
  2. Best Goggles for Open Water Swimming and Triathlon [34.6]
  3. 10km training schedule – 3 months out [11.1]
  4. Waterproof MP3 players for swimming [9.4]
  5. Diana Nyad’s Directional “Streamer” [7.9]
  7. You might be an open water swimmer if … [6.1]
  8. Recommended Products [5.8]
  9. The Animal Set Thread [5.8]
  10. Swim Videos [5.2]
  11. training for a 5km swim [5.2]
  12. Manhattan Island Marathon Swim 2013 [5]
  13. What is an appropriate weekly mileage for completing marathon swims? [4.6]
  14. Sunscreen?! [4.5]
  15. Warming up after a cold water swim [4.3]
  16. Driven [4.2]
  17. Open Water Blogs [4.2]
  18. Diana Nyad’s epic swim [4]
  19. What type of Garmin is recommended for tracking distance and time of open water swims?

A better SWOLF formula

A better SWOLF formula





Marathon Swimming Rules Survey: Results and Analysis

Marathon Swimming Rules Survey: Results and Analysis

Marathon swimmers talk a lot about rules – what should and shouldn’t be allowed during a swim – but as far as I know, there has never been any systematic study of what marathon swimmers actually think, as a matter of public opinion.

Perhaps most would agree that goggles are OK, and fins are verboten… but what about swim streamers and stinger suits? Or drafting off the escort boat? If you only read blogs and forums, you might assume the most vocal opinions represent the majority. But do they really?

Earlier this month the SBCSA launched a survey to find out. Over 25 days, we received 175 responses from around the world.

First, a Summary of Findings (TL/DR). Click any of the following links to skip directly to the relevant section.

I. We received responses from a representative sample of marathon swimmers – current, former, and aspiring.

II(a). Marathon swimmers agree on basic channel-rules attire: traditional porous textile swimsuit (including jammers), goggles, one latex or silicone cap, ear plugs, and nose clips.…


Google search trends and open water swimming

Google search trends and open water swimming


Is open water swimming “growing”? 

search term: “open water swimming”

Some observations:






What is the speed advantage of a wetsuit?

What is the speed advantage of a wetsuit?

Everyone knows wetsuits help keep you warm in cold water. Lesser known among the general public (but well-known among triathletes) is that wetsuits also make you swim faster! The buoyant neoprene in a wetsuit floats a swimmer higher in the water, decreasing drag and thus increasing swim speed.

But how much faster is a wetsuit? I’ve heard various rules of thumb: 10% speed increase; 4-6 seconds per 100m; 1 minute per kilometer. I’ve also heard various caveats: it depends on the swimmer’s skill (better swimmers benefit less); it depends on the swimmer’s body-type (naturally floaty people benefit less); it depends on the quality of the wetsuit (you get what you pay for); it depends on the fit of the wetsuit; and so forth.

So the answer is: It depends. Because I’m usually disinclined to let things go at “it depends,” I decided to conduct a field experiment. Reef & Run, which I’ve written about previously, provided the perfect laboratory. Almost every Thursday evening between June 21 and yesterday, August 23, I swam one mile in the ocean at East Beach in Santa Barbara.…