BMW seats are far easier to remove than most. You don’t want to remove the seat back, just the cushion. Just push back slightly on the front edge of the cushion about 6" in from the door. Sometimes I do it with my thigh with my knee on the floor, but yours is wet. At the same time, pull up on the front lip of the seat. Repeat for the other side. Once the front edge is popped up, pull forward so that the rear edge is clear of the seat’s back. Lift.