http://breezewiki.bunny5exbgbp4sqe2h2rfq2brgrx3dhohdweonepzwfgumfyygb35wyd.onion/minecraft/wiki/Soul_Sand
However, these collision boxes have an effect only if entities are clipped into soul sand. If a water current is pushing the player diagonally against a wall and soul sand is the block adjacent to the player's head when the current ends, it causes the player to jump.