Forget board shorts, the only thing Allen Iverson needs when he hits the waterpark is JEWELRY ... and TMZ Sports has the pic to prove it.

The NBA legend hit up the Great Wolf Lodge in Virginia recently ... flossin' like a G ... with 3 gold chains, a Playboy shirt, and a gold-trimmed Detroit hat to match.

Our waterpark sources tell us A.I. spent two days at the Lodge ... and was with a group of roughly 20 people ... though it's unclear why Iverson and company decided to take the trip.

... other than the fact IT'S SUPER FUN!!!

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