Cam Shaw -- an undefeated boxer from the U.K. -- tragically passed away this week ... after drowning while snorkeling in the Great Barrier Reef in Australia.
He was only 25 years old.
The 4-0 featherweight fighter and his girlfriend met up with two of his friends in Cairns -- the gateway to Australia's Great Barrier Reef -- for a snorkeling experience on Monday.
Unfortunately, Shaw drowned during the expedition.
A Queensland Police spokesperson says Shaw's death is under investigation ... but "it is believed non-suspicious.