This is the greatest marriage proposal fail ever … when a bride gets so excited she hits the gas of her powerboat … sending her would-be groom flying in the air.

Check out the aspiring groom walking on the back of a boat … lasering in on the unsuspecting bride-to-be who is on another boat … separated only by a foot or so.

He pulls out a ring and she’s super shocked, exclaiming, “Oh my God!!!”

Now the buzzkill. He leans in for a kiss and she accidentally hits the gas pedal.  Her legs kick up in the air, hitting him as he falls off the boat in hilarious fashion.

We’re guessing since she was obliging with the kiss, she said yes.

Hey … way more memorable this way.