Complex sentence: Other acoustics activities in the ocean may not so benign insofar as marine mammals are concerned: air gunshots for geophysical surveys, and some of the louder transmissions by the U.S. Navy for various purposes are documented to present a threat to marine mammals.
Split into simpler sentences: Other acoustics activities in the ocean may not be so benign insofar as marine mammals are concerned. Air gunshots for geophysical surveys, and some of the louder transmissions by the U.S. Navy for various purposes have been studied as potential threats to marine mammals.