A jet ski operator is lucky to be alive after he slammed into a dock at full throttle ... and it seems a particularly difficult stunt caused all of the problems.

Dillan Stapler -- a jet ski influencer who is part of the "Lanier Crew," a group of jet skiers based out of Georgia -- shared a video of himself running straight into a dock.

Check it out ... he crashed at full speed and is jettisoned off the jet ski -- landing in a heap on the unforgiving wood.

Stapler's pulls him from the water ... and he looks totally lifeless -- held above water only by his life vest and his pal.

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Stapler explains on TikTok he apparently passed out after climbing onto the front of his jet ski to operate it from the vehicle's "hood." Video taken from behind shows him go limp ... and he's lucky he didn't fall off and get dragged under the jet ski.

He says this goes to show even professionals need to be careful ... after all, jet skis may look like toys -- but they go pretty darn fast!