A jogger noticed his body floating in the water just off shore near 700 South Lake Shore Drive.
His family and friends say Dennison's death might have been an accident.
"We don't suspect foul play because of the condition of his body he wasn't beaten up badly and he did have his wallet with his credit cards. We don't think it's that but we don't know what to think that's why we are anticipating the autopsy report," said Tony Libri, friend.
Those autopsy results are expected sometime on Tuesday.