LeBron James -- Chasin' Waterfalls ... On Family Vacay (VIDEO)

LeBron James is not sticking to the rivers and lakes that he's used to -- instead he took the whole damn fam on vacation to Hawaii, and had a run-in with a waterfall that had him grinning from ear-to-ear.

The whole James gang ... including mama Gloria and her rapper fiance' Lambo ... are over in Kona, Hawaii, and so far the highlight of the trip is this tropical dip.

LBJ's got a lot to celebrate -- a bonafide Hollywood hit with "Trainwreck," and a lucrative new development deal with Warner Bros.

It's always good to the be king (except sometimes in the NBA Finals).