Heidi Klum Goes Topless at Beach, on Video

Heidi Klum decided to strip all the way down before taking a dip ... throwing off her bikini and going for a topless swim in a new video.

The model shared a video to Instagram Sunday in which she's wearing a thong-style bikini and new top ... proving that when the sun is out, it's more than her buns she's busting out.

Check out the vid ... Heidi takes her model walk from the runway to the beach -- striding down the sand toward the ocean.

She goes in about knee-deep before the video cuts off. Klum captioned the post, "Let’s dip" -- and, we know a whole lotta fans who want to take her up on that offer.

Klum's talked about ditching her top in the past ... revealing in an interview last year that her kids feel the need to remind her to put on a top when their friends come over to the house.

Heidi's daughter, Leni, told Alex Cooper on the "Call Her Daddy" podcast that it's actually created some embarrassing moments over the years.