Lamar Jackson Terrifyingly Tumbles Over Jet Ski In Beach Football Sesh

File under: Things Your Superstar QB Should NEVER Do!

Here's video footage of Lamar Jackson tumbling over a jet ski and into ocean water in a beach football game over the weekend ... and we gotta say, it's terrifying!!!

The NFL MVP was getting in a little run with his bros on the sand ... when he started doing Lamar Jackson things.

The clip is pretty crazy ... Jackson's acceleration from zero-to-sprint is INSANE -- but when he finished off the run, John Harbaugh and ALL of Ravens nation couldn't have been happy.

Check out the clip, Jackson tumbled and dove headfirst over a waverunner ... and it's maybe the scariest hit he took in all of this past calendar year.

Fortunately, LJ came up from the fall just fine ... but, man, SHEEESSSSHHHHH!!

Of course, beach football injuries are VERY real ... remember, star NFL running back Robert Edwards completely shredded his knee in an infamous sand game back at the 1999 Pro Bowl.