Okay, something is going on with the server, I'm getting an internal exception: java.net SocketException:connection reset.
I was letting the water, which I had removed the source blocks of, go down, so the lag shouldn't be increasing or anything.
Edit: When I moved out of the area, the problem stopped. It was also when the night vision potion ran out, so I don't know if it was me moving out of the area or the potion that was causing the problem.
Edit: Also, the area seems to be glitching out and thinking that there is a wither nearby when there isn't, not sure, and lighting bugs galore