Complex sentence: Dave has also owned a Cis-Lunar Mk5P that he used on extended dives in caves that are shallower than 150 m. The Cis-Lunar has greater redundancy capabilities he believes for such dives, but cannot cope with extreme depths.
Split into simpler sentences: Dave has also owned a Cis-Lunar Mk5P that he used on extended dives in caves that are shallower than 150m. TheCis-Lunar has greater redundancy capabilities he believes for such dives, but cannot cope with extreme depths.