Entity update lag, cows floating when hit

After playing for a while (I was exploring for about an hour), entities start to get seriously laggy.

I hit a bunch of cows, and they started to float, then rise to "jump height", then fall down, like 1 second between each step. Then they would sprint extremely fast and get the damage.

It happened for multiple mobs (also bunny).

Also boats were getting strange glitches and would eject me and not let me re-enter, but not sure if related.