I've also observed this happening. In Armani's case, I'm going to assume that he first observed it happening in stable 12.12.5, just like me, as I believe he said that he noticed it happening on his level Natural Born from a few LDCs ago. However, in my case, I got completely taken by surprise with this while I was solving 400 metres 3 -
The infernal moat (now at 400 metres 13 due to me giving David feedback that the level's way too hard for the third position of the rank) of DavidLems off-camera a few weeks ago. The level has the water pit at the bottom, just like Armani's post.
I can go a bit further than this. I have confirmed that it happens anytime the wall or the water pit is 4 pixels or less in height and that the water pit doesn't necessarily have to be at the bottom of the level. See attached level, where there is also a water pit at the top. Assign the swimmer skill to a Lemming at the top. He will just fall through that water pit instead of touching the water and swimming. However, he will correctly hit the water pit at the bottom and start swimming. If you don't assign the swimmer skill to a Lemming at the top, he will touch the water at the top and drown just like in Armani's case with the water pit at the bottom.
You can do the same with assigning the swimmer skill to Lemmings at the bottom, but same observations: A non-swimmer will touch the water and drown, while a Lemming who has the swimmer skill doesn't touch the water and falls through the water pit.
Here, my guess is this bug has something to do with the changed swimmer physics of 4 pixels being the cutoff point that determines whether a swimmer will dive underneath or climb if he's a climber:
https://www.lemmingsforums.net/index.php?topic=5346.msg89674#msg89674In any case, a fix is definitely needed, as this is quite odd and inconsistent.
