May years ago, I was on a trip across the Indian ocean, and on very calm days (and I mean no wind at all), we would jump in and out, lather up and wash and jump in again, and then use about one cup of fresh water each in a pressured sprayer to rinse in a fine mist...one time there were 4 of us in the water splashing around and I was inspecting the hull with a mask...Usually there is nothing out there in the big blue, but suddenly I saw lots of small fishes, and a second later a head on view of a 6 to 7 ft shark...about 3 or 4 metres away...that was only for a split second before I screamed shark at everyone and raced back to the ladder to get out...everyone else thought I was joking till they saw a fin and then it was a mad scramble to get out...After that, the shark hung around and we tried to catch it using corned beef of all things..
we had it take the hook, on a handline..(gloves)...but we lost it..
(I was only 19 at the time)
Since then I have sailed the Atlantic 3 times, the Pacific and a few other places, and have often swum around the boat, sometimes to fix something other times for fun...just not for very long...5 minutes at the most..- so I guess if you are going to do it, give yourself a time limit..
- it takes a while for a shark to discover the source of the disturbance.