[freetime2]

Yup I think it's really easy to overestimate your swimming ability. The first time I swam laps in a 50m pool, I remember being really surprised at how much effort it took to swim the length of the pool. And after about 500m or so I got a cramp in my leg.

If I were 500m from shore, weighed down by clothing, and dealing with waves and/or currents, that could be a disaster.