Author Ellen Prager is Chief Scientist for the only operating underwater scientific habitat in the world. That for me was the most surprising fact in the whole book, considering there were dozens of such habitats in the 1960s.
Prager recounts her own adventures and explains the importance of various branches of marine science. She is not a transcendent nature writer like Sy Montgomery, but her enthusiasm comes across well. Page 85 mentions the observation of a yet-unidentified 2m-long squid. A small but surprising error is her claim that we have no submersible vehicle today, manned or unmanned, that can reach the depths Piccard and Walsh pioneered in 1960, but on the very next page she mentions Japan's Kaiko, which does exactly that. Prager repeatedly returns to the need for scientists to gather data in the field and the importance of the scientific method. This slender volume (151 pages of text) is a useful addition to its genre that hopefully will inspire some of the marine scientists of the future.
UPDATE: Dr. Prager wrote in to correct me on the supposed error, reminding me the original Kaiko was lost and the replacement ROV is limited to depths of 7,000m. In 1995, the original Kaiko dove to 10,911m in the Mariana Trench. This is approximately equal to the record established by Piccard and Walsh in their bathyscaph Trieste, with some uncertainty due to improper calibration of the Trieste's instrumentation. Richard Ellis' Deep Atlantic (Knopf, 1996) is one good source for an account of the two vehicles' dives.