The prolific Winton (The Riders, 1995; etc.) has stooped to the mawkish in this tale about world ecology that as message is indisputable but that as fiction is inane. Abel Jackson's forebears were whalers, his father a pearl- diver whose life was ended by a shark. When this tiny slip of a story opens, Abel is ten years old and living a life of hard but edenic subsistence with his mother on the family property that's squeezed along the coastline, a national park behind it, the bay, headland, and open sea n front. Part of the pair's income derives from snorkel-diving for abalone off Robbers Head, and it's a sign of the times when, after the good abaloner Mad Macka dies of a heart attack, he's replaced by the villain Costello, a rapist of the sea (unlike the good Abel and his mother, who take ``a couple of abalone from each clump, leaving the rest to breed and grow''). Costello is run off by the law after a heroic and admittedly dramatic intervention by Abel and his mom, but there are other woes in store for the sea. ``Things aren't the same, Abel,'' says mother. ``It's getting harder to hold on to good things.'' After unexplained fish kills (``The ocean is sick,'' says mom. ``Something is wrong''), Abel determines that he'll go ``to university to figure out the sea.'' His international career as a marine biologist takes him far from home, mother, and the enormous, blue, friendly groper he played with off Robbers Head throughout his boyhood. But age, time, and another disaster will bring him back forever to care for mother, baynow declared a sanctuarywife, and new family. Psychologically and in every other way a YA, though apparently aimed at an adult trade audience. Pretty writing (a baby girl has ``fists. . . like pink seashells'' and ``cried like a bird'') helps offset the simplistic elements of the whole.