Private-eye Loren Swift (Hardball, Foul Shot) of Charlottesville, Va., has now, along with girlfriend Patricia, taken up scuba-diving as a hobby. And this fourth, so-so outing gets underway when--on their first real dive, in a local abandoned quarry--the couple finds an underwater corpse in diving gear, wedged between the rocks 80 feet down. Accidental drowning? Absolutely, according to the cops--who figure out that the dead man, rich young realtor Eric Vessey, ran out of air and panicked (a common scuba-diving scenario). Vessey's twin-sister, however, sure that Eric was murdered, hires you-know-who to investigate. So Swift is soon following three overlapping trails: Eric's involvement with a psychic-research institute, which owns the quarry site; his search for a fortune in gold, hidden somewhere in that quarry by a 1930's bootlegger (whose murder was never solved); and his tense relationship with twin-sister Morgan and brother Drake. Along the way, of course, Swift is attacked by enigmatic assailants--one of whom shoots Swift's visiting brother Ashley (a boozy poet) by mistake. There's a long scuba sequence in which Swift bravely (dumbly) uses himself as bait to trap the killer. And, after a sluggish buildup, the denouement offers a couple of out-of-left-field twists. Still, though overplotted and creakily paced: hard-working, semi-satisfying detection, given a bit of bounce by Swift's easygoing, half-cynical, half-sentimental narration.