Deep Green

This submersible has no visible tools.

It does have this big bulge in the bow.  That would imply some kind of large sonar array inside.

Such a submersible could be used to map undersea canyons.

Such knowledge would be useful for attack and missile submarines if they were trying to hide from detection.

It could also have a grapple arm stored in the bulge that deploys only when needed.

These vessels can also use many different kinds of sensors to determine depth, currents and other hydrographic data that could have scientific, military or commercial uses.