I had a turtle problem too.I made a trap out of 4" sewr pvc and goat fence.Get a 10 ft sick of pvc and cut into 4 equal lenghts,then glue together with 4 90 degree couplers.cut the fence about 12 to16 " tall and attach to the outside of your float.Cover the bottom and make a ramp with same fence and attach it to one side.the turtles will crawl on it to sun and fall in,but cant get back out.Regular pvc will work but its pretty heavy,especially with 37 turtles in it.If you want to catch smaller turtles cover the outside with chickenwire.
Good luck Tom

I subscribe
Some days you get the dog,and some days he gets you.Every dog has his day,and sometimes he has two!