THE UNDERWATER reaches off the California coast are among the most important U.S. energy fields still largely unexplored. For five years they have been a major battleground for the Reagan administration, the energy industry, the California congressional delegation and environmental groups. President Reagan's first interior secretary, James Watt, tried aggressively to lease the tracts for drilling. Congress responded with a moratorium in each of President Reagan's first five years on any leasing off the California shore.

This year Mr. Watt's successor once removed, Donald Hodel, tried to break the impasse. In July he reached a "preliminary agreement" with members of the California delegation. The government has divided the seabed off California into 6,460 nine-square-mile tracts. Under the agreement 150 of these, mostly off the northernmost part of the state, could have been leased the rest of this century; the others were reserved.

The agreement met instant resistance from the oil industry, on grounds it was a break with administration policy that would lock up almost the entire coast. The industry argued that in a time of trade imbalance and continuing energy uncertainty, it made no sense to put a large potential pool off limits. Energy Secretary John Herrington also put an oar in. Cabinet officers rarely air their differences in public, but Mr. Herrington, whose responsibilities overlap with Mr. Hodel's, said that he did not regard the compromise as "in the best interest of America's energy future." A somewhat embarrassed Mr. Hodel has now renounced his well-intentioned handiwork, saying it was never more than tentative and that he has learned it would have walled off more choice tracts than he originally supposed. The indignant Californians with whom he negotiated are meanwhile trying to reimpose their moratorium. It is not clear they can; a major environmental issue has been added to Congress' already crowded agenda.

The problem in all this is that Mr. Hodel, who now seems to have been chopped up in the process he began, was right. A moratorium is not the answer to the leasing issue any more than is the open season the oil industry apparently would prefer. If there indeed are important amounts of oil and gas off California, sooner or later they will be drilled. Except in the rarest cases, no mix of California and environmental interests will prevent that. The questions are when and how, not whether.

This is federal oil and gas, publicly owned. From the standpoint of national interest, does it make more sense to drill for it now or hold off until some time in the future? Should America use up its own oil first or someone else's? In any case should tracts be put up for lease in a time of glut, when return to the government will be low, or saved until copmanies are likelier to bid full value? Leasing decisions ought to be governed in part by a coherent national energy policy. These have not been. Congress, Mr. Hodel -- and Mr. Harrington if he is of a mind -- ought to go back to the bargaining table.