The journey is across the bottom of the Atlantic ocean on foot as young Josh Sparke, his father and ichthyologist Wayne Markham become ""manfish"" a state that is about as believable as the rather watered down characterizations. But this ""inner space"" exploration offer plenty of excitement with mud avalanches, undersea earthquakes and tidal waves, sharks, whales and even an enormous grouper that becomes first a mascot, then a threat. At one point Josh is lost in an immense underground cavern, at another he's buried alive, and still later he's being swept along at over a hundred miles an hour. The pressure isn't just a matter of depth: there's a deadline that they almost miss as the year's supply of air runs out. The somewhat dubious adventures are offset by the number of interesting facts worked in -- ""each codfish lays as many as 9,000,000 eggs at one spawning,"" -- for those who are interested.