I've also swum in lakes besides Saranac Lake, which I mentioned above- specifically, Lake George, Lake Champlain, and another small lake in the Adirondacks. I think the scariest things I had to worry about were snapping turtles, but I've never heard of someone getting attacked unprovoked by one in the water. Then again, maybe Giant Water Bugs are called "toe-biters" for a reason... and once, when we were hiking around a small pond, we saw a big leech swimming along. I didn't actually swim there.
I haven't been to Hawaii, but one of my sisters was, and she said the schools of small fish were amazing. I don't know if she actually went swimming there, though.
It's kind of gross when you're wading in shallow water where the bottom is soft mud, though.
@SuicideBlonde I love manatees, but I've never seen one in the wild. During one of my Florida trips, someone told me I had just missed seeing one. I know it's against the law to approach a manatee even if they seem friendly, and that this is for the manatees' protection, but it would have been amazing to see one- even from a distance.
@Emma JC "
...just when you thought it was safe to go into the water..." (the camera shifts to a remora's-eye view from beneath a swimmer)