The Fort Bend County Sheriff's Office said it was called about a possible drowning around 7 p.m. at the 24-Hour Fitness at Bella Terra, just off FM 1093.
When deputies arrived, they found a man hanging on the ropes inside the pool.
The man was rushed to the hospital, where he was pronounced dead.
Deputies said it does not appear foul play was involved in the man's death.
The medical examiner will now have to make its determination in the official cause of death.
The gym has since reopened after deputies completed their investigation.
ORIGINAL REPORT: Body found in pool at Cinco Ranch-area gym
Incident: @FBCSO investigating a reported drowning at 24-Hour Fitness - Bella Terra (SH 99 / FM 1093) 72 yr old male. Male was swimming alone and situation does not appear to involve foul play.— Major Chad Norvell (@chad_norvell) February 6, 2018