When I boarded the Bottom Scratcher the night of August 24, the first thing I did was plug in my phone and activate the Instamapper GPS tracking app.
Why was this the first thing I did? As most of my readers must know by now, I have as much fun (probably more fun, actually) analyzing marathon swims as actually doing marathon swims. Hence my six-part MIMS report.
As usual, the data tell an interesting story. The yellow path shows the GPS tracks of the boat which, except at the start and finish, was between 5-25 meters off my left side. The red line shows the straight-line “ideal” path between the start and finish. The white placemarks are self-explanatory.
I covered the first 5 miles in 2:06:50 (25:22 per mile), my fastest pace of the swim despite big swells and chop throughout the night. I was 12 minutes slower for the second 5-mile chunk (27:44 per mile), probably because I was plowing through the same waves and chop, but with substantially less fresh shoulders.
I hit the halfway mark (10 miles) at 4 hours, 25 minutes. So, contrary to our calculations at the time, I actually wasn’t on pace for a low-8 hour swim. In fact, I was on pace for pretty much what I ended up with – just under 9 hours.
In the second half of the swim I ran into the strong NW-to-SE cross current that had bedeviled many recent Catalina swims. Notice how my tracks “bow out” to the right of the “ideal” path, especially around 15-16 miles. The current is pushing me away from the finish (toward Long Beach), and the boat is forced to turn almost due north (against the current) to hit Point Vicente.
Despite the adverse current I held my pace steady – 2:13 (26:42 pace) for miles 11-15 and just under 2:17 (27:22 pace) for miles 16-20 — including some slow kelp crawling at the end. Indeed, my two 10-mile splits were within 5 minutes of each other: 4:30:28 vs. 4:25:31.
The difference between my slowest pace and fastest pace – about 2 minutes per mile – corresponds well to my subjective experience. Though, the pace itself (25-27 minutes per mile) is much slower than my typical pace in a pool (or neutral open-water conditions). For the first half of the swim it was the chop. For the second half it was the currents. In both cases I was slowed by, I’d estimate, 2-3 minutes per mile.
To be continued…