[Maleficus]

Best suggestion:

Just before the start of the tunnel, have a node very close to the surface that will encourage the bot to come up for air before heading into the tunnel. This way their air supply will be full when they enter the tunnel.

Then, for EVERY air pocket, have a node that leads up to let them breathe.

The problem is, that they are prolly pretty low on air when they actually enter the tunnel (maybe they've been under the water for a few seconds already, fighting or whatever), and they start to run out of air and try to swim up to get some, but get stuck on the walls.

The swimming support is pretty basic, and they sometimes need a little help being shown where the air is.