Complex sentence: Atmospheric diving suits may be used to isolate the diver from high ambient pressure, and although not always recognised as a mode of diving, crewed submersibles can extend depth range, while remotely controlled or robotic machines can reduce risk to humans.
Split into simpler sentences: Atmospheric diving suits may be used to isolate the diver from the effects of high ambient pressure. Although not always considered to be properly a type of diving, crewed submersibles can extend depth range, while remotely controlled or robotic machines can reduce risk to humans.