So, when you are crouching on top of a trapdoor, that's on the bottom part of a block that's above the water (as seen in the video) and put another trapdoor on the same height in front of you while crouching, a weird bug happens where it loops the water splash sound and makes the game think you're under the water for a very brief moment. And it keeps looping until you jump and stop crouching or go to a nearby full block. Idk if it happens to other blocks too, as it happened on accident when I was playing survival.