I started a 1x16 fortress (using nanofortress) which was all over the ocean apart from one tile, sso I could try and build a huge bridge over the ocean. The fortress ran perfectly, with no lag whatsoever. The ocean was something like this:
XXXXXX X = land
777777777777777777777777777777777777XXXXXXXXXXXXXXX
77777777777XXX7777777777777777777777XXXXXXXXXXXXXXX
7777777777XXXXX777777777777777XXXXXXXXXXXXXXXXXXXXX
7777777XXXXXXXXX77777XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Nothing wrong with that at all, so I just played for a while...lalala...playing...dwarves are all dying of thirst...miasma from all the corpses...people are jumping into the ocean...I'm out of barrels...my brewers are dead...abandoned the fortress.
But then something bad happened.
I went back there as an adventurer, and there was nauseating lag. I managed to get further up the bridge, but then noticed that the sea was a lot lower than usual. Then I realised that the sea was now like this:
XXXXXX
121 XXXXXXXXXXXXXXX
1112345667677XXX7777777777777777777777XXXXXXXXXXXXXXX
7777777777777777XXXXX777777777777777XXXXXXXXXXXXXXXXXXXXX
7777777777777XXXXXXXXX77777XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
When I was searching around the bug report board, I found
this - I'm not sure if it's the same problem.