I was going for a ride on my boat, and I entered a chunk that wasn't loading (causing a massive lag spike, that's another unrelated issue I'm having that I've seen discussed before) And then my boat was underwater and I was nearly drowning. Conveniently landed right over a shipwreck, so I guess it's not all bad.
You're probably in a bubble column, boats sink in them. (Note the bubbles in the first screenshot)Examined the screenshots, no bubble columns.