Law enforcement officials in Homer, Alaska tell TMZ they got a call at 12:52 p.m.Tuesday reporting a deceased male at the Best Western Bidarka Inn.
Upon arrival they found 33-year-old Tennison lying on a bed unresponsive.
TMZ was told a search of the room -- which was registered to Tennison -- turned up a small amount of marijuana, as well as several bottles of alcohol in the refrigerator.
Police tell TMZ they believe there had been a party in the room the night before.
It's unknown if the booze and drugs played a role in Tennison's death.
His body was transported to the State Medical Examiner ... and an autopsy is scheduled for later Wednesday.
Time Bandit captain Andy Hillstrand posted on his Facebook page that Tennison had served as an engineer aboard the fishing boat during the off seasons, and just joined the crew as a deckhand a few months ago for the crab season.
He also wrote on the official Time Bandit website that "Justin was tough as a bull and was an all-around good hand. The Captains and Crew appreciated his hard work and many contributions this past year. We will miss him terribly and wish his family all the best during this most difficult time."
Tennison had two children, according to Hillstrand.