DOWN AT OCEAN CITY these days, the most immediate problem for most people may be finding their place on the beach. But the sand and the sea pose much larger problems for this booming resort - and for the taxpayers, too. Mayor Harry Kelley and other officials have spent millions fighting beach erosion over the years. Now nature's threats may be growing worse. A new study has found massive erosion of the ocean floor, starting about 200 feet offshore. That could make future storms even more harsh and damaging.

Of course, Ocean City has challenged nature from the start. It sprawls along a barrier island, and such sands don't naturally stand still for multi-billion-dollar development. Left alone, the Atlantic beaches erode here, build up there, and gradually migrate south and west. That makes seaside building a chancy business. Traditionally, it has been shored up by massive public and private attempts to "stabilize" the sands. But experts increasingly agree that fighting the Atlantic is a losing game, doubly so because erosion control projects may actually accelerate erosion or, by blocking the normal paths of high water, increase the fury of storms.

The National Park Service recently decided to stop resisting erosion along its segments of North Carolina's Outer Banks. The Army Corps of Engineers has abandoned a $500-million plan for huge sea walls and jetties on the New Jersey coast. But at Ocean City and other densely developed areas, it is too late to warn investors off. Instead, state and local officials are advocating two more attempts to tame the surf: an interim system of groins and jetties, which could cost from $9 million to $15 million, and a more elaborate, $44-million Corps of Engineers program for preserving the beach.

Something probably must be tried, though with the understanding that it may not work very well or for very long. But who should pay? Erosion control has generally been a job for the Corps. Yet the federal government and taxpayers across the country did less to foster the Ocean City boom than state and local government - especially Worcester County, whose taxpayers have benefited immensely from the levies on all those condominiums. They certainly should bear part of the cost. So should the developers. People who seek profit on seashores, as in flood plains and earthquake zones, should not expect the government to immunize them against loss.