Yeah, I thought about that- my experience was in warm water, but we did have certain infrastructure pre-programmed to avoid. We'd call it geofences today, but I

Yeah, I thought about that- my experience was in warm water, but we did have certain infrastructure pre-programmed to avoid. We'd call it geofences today, but I'm not sure it had a term then. You could hope for a semi-operable abort, and leave an acoustical beacon out to the side of the glacier to home on. Sort of a "proceed to x, then abort to surface". There are stories though, of when the navy was initially testing this tech ~20+ years ago, of having to basically keep mini-subs and full time salvage crews on standby, for all the times the things would get their nose stuck in the mud. They quickly came up with a front facing acoustical Doppler sensor for terrain collision avoidance. Even then, it sometimes backfired, like steering up into the face of a cliff, instead of turning laterally. But maybe that's the reason for the /rov tethered configuration.