As reported in my Reddit post:

https://www.reddit.com/r/NintendoSwitch/comments/8u3dri/its_been_almost_a_week_with_the_new_minecraft/

Swimming. Feels like you left the beta code in. Your air supply display goes completely away at times. You don't know if you have air or not. And I have also found myself swimming across land. So you pop out of the water, glitch and next thing you know you are now swimming across a forest floor. Most of my play has been multiplayer with my group who also are all on the Switch but more than one of us have found ourselves swimming on land. Elytra has some of the same glitches at times, but at least those I am pretty sure are lag. I did some singleplayer swimming and while it's better, it's still not as smooth as I would hope it would be. Lag in multiplayer is definitely ruining the experience.