Your seatbelt is your best friend in a crash, but in water, it’s a needy ex you need to dump fast. Unbuckle it now. Don’t wait until the water is at your chin, because then you’ll be fumbling like a toddler in mittens.
If the buckle is jammed? Slide out from under the strap. Or use a seatbelt cutter (yep, they make those—keep one in your glove box like a tiny superhero gadget).