Manvel police told ABC13 Eyewitness News they received reports around 4:20 p.m. of a man who was lost in the water.
Authorities say the man was with a group of 15 others at the Twin Lakes RV resort.
Investigators said the 24-year-old man was swimming with two other people to a trampoline float when he became tired and went under.
The two men he was with attempted to recover his body, but they were unable to reach him.