It's a good question.
We're wondering the same for our beach event next month. There is a total prohibition on being even close to the beach except for the landing strip - but if someone has a donkey-stop are they going to plonk in the sea or try and glide to any part of the long, flat (but busy) hard sand of the beach?
My suspicion is that, regardless of what anyone writes here, most/all would head for dry land and justify it with "I'll aim between the people, it'll be fine".
There have been a number of beach forced landings over the years, not seen any occasions where the pilot chose for the water.