BT500 tracked subsea trenching machine for underwater cables. It can operate at depths of up to 1,000 m (3,281 ft).
https://s3-us-west-1.amazonaws.com/h...a_trencher.jpg
https://www.youtube.com/watch?v=cnrA1HelAWI
Previously:
https://www.homemadetools.net/forum/...550#post132368
https://www.homemadetools.net/forum/...017#post125375
https://www.homemadetools.net/forum/...1676#post94385