All I can say is Eeeewww!

[Alex]

Ever swam the water part of a triathlon? The stuff under the water isn't really so relevant since you're already getting thoroughly thrashed by the people in the water with you.

Really, as I think about it the logistical concern I see is that while they will certainly have a way to get everybody out of the water I don't see any way they can engineer one where it will be a smooth continuous movement like hitting the beach of a pond. And if there is a backup of swimmers they're going to run into trouble pretty quickly.

But I assume (or hope anyway) that they've go somebody experienced enough in planning to be thinking it through.