'Deadliest Catch' Captain Busted for Bad Pot ... Of the Crab Variety

"Deadliest Catch" captain Sean Dwyer was in hot water after officials discovered his crab fishing gear wasn't up to par ... TMZ has learned.

According to court docs ... Alaska's Fish & Game officials busted Dwyer for having a crab pot on the F/V Brenna A with an undersized escape mechanism. For you landlubbers -- crab pots must have an 18" hatch held closed by biodegradable ties. It's designed to give crabs a chance to escape pots that get lost at sea.

We're told Dwyer's escape hole missed the mark by 3 inches. The fix only required one snip of twine, but it still cost him $1,500 in fines, and now he's on probation for 2 years.

Gotta mind your holes up in Alaska.