In the single player Pure survival save, if you shift to the edge of the water, you can double click the space and press back immediately. If you press the space and press Back continuously, you can open the Elytra while standing upside down (as if lying down) in the water. Then you can press the Forward button to use the Elytra while swimming, and you can use fireworks to directly leave the water or fly quickly in the water Can lie on the surface or feet on the surface without losing oxygen