Dr. William Beebe is a celebrity in the world of explorers, a charismatic scientist and naturalist who was mentored by President Theodore Roosevelt himself. It’s the early 1930s, and he hopes to dive deeper into the ocean than any believe possible and observe deep-sea aquatic life. To do this, he will use a new, pressure-resistant diving sphere invented by Otis Barton that Beebe dubs a bathysphere.The only caveat to using this hollow, round submersible is that the fame-hungry and adventure-seeking Barton will join him in his dives off the coast of Nonsuch Island in Bermuda. But perhaps as important as the difficult Barton and his steel ball is the relatively unknown commercial artist the explorer employs on this journey—German-born American Else Bostelmann. Bostelmann expertly depicts the wild undersea creatures Beebe witnesses, and her work appears in numerous publications, like National Geographic, raising her profile considerably in the arts, sciences, and even the fashion world. But the very shrewdness that makes her such an astute artist also makes her question many things about the doctor—his paradoxical nature as a conservationist who hunts, his fraternizing with eugenicists, his affairs with the younger women who work for him, and, most concerning to her, his apparent addiction to facing danger for his studies. Politsch shows an enthusiasm for his famous characters’ exploits that rivals Beebe’s own excitement over the bioluminescent fish he discovers. Scenes depicting the preparation and testing of the bathysphere are as engaging as when it finally makes its first dive. The claustrophobia of the ball’s 4-foot-6 diameter is palpable; an errant electrical spark or a creaking winch is downright anxiety inducing. The book takes its time, whether capturing little moments of beauty on Nonsuch or fleshing out lesser characters who are a part of Beebe’s team, a nice distraction from the long, sometimes tedious waits between dives.