When standing on the block directly below a door/trapdoor, player will get in swimming animation if they toggle the door/trapdoor.

When you stand on the block where a door/trapdoor is placed and try to close/open it, you will sometimes get in swimming animation depending on your position on the block. You can easily get out by walking (swimming) out or by toggling the door/trapdoor again. Breaking the door/trapdoor and/or the block below the door/trapdoor doesn't fix the problem. Works with wooden and iron doors/trapdoors.