Any health precautions for lake swim?

Well, drowning should be a concern.  It takes a lot less than 4 feet to drown in.

Unless the lake is notoriously polluted, I can't see any (other) reason for concern.

thanks

Getting hit by watercraft?

avoid gators, snakes, and snapping turtles...
oh, and those huge catfish that scavenge the depths...

Oh, and gar are quite common in shallow lakes, and yeah, they suck. Definitely a health precaution!

Wasn't there an article on cnn about a boy being "eaten alive" with lake bacteria?  I didn't read it, but I saw the headlines.  This isn't the first time I've seen a headline like this. 

E coli.  We have a lake here that we have open water swim practice in every week, and they have to test the water the day before to make sure the e coli levels aren't too high.