What is new is that nearly 6 billion of us are putting pressures on the natural order that sustains us. The life-support functions of earth's oceans are burdened with oily ballast and other wastes dumped overboard from millions of motorized vessels and pollution flowing from the land and air into the sea, along with millions of tons of hard trash. Oil spills are among the most obvious forms of pollution, but attention is shifting to less visible contaminants, especially the flow of excess fertilizer and other chemicals that are applied to crops, lawns, golf courses, fields and parks.

Last year for the first time, the World Conservation Union listed many marine creatures as "threatened," most of them commercially important species of fish, including Atlantic cod, bluefin tuna and swordfish. Finding fish--once an art--is now highly mechanized and precise. Every last fish in some populations is targeted and scooped into giant nets that do not distinguish between young and old, male and female, this species and that. If such techniques were used to capture birds, foxes and deer, chances are that we would have long ago given up fishing for them because of the obvious destruction and costs involved with dragging nets across fields and forests. However, few of us get to see that a scallop dredge or shrimp trawl is to the sea what a bulldozer is to a forest.

Despite the obvious dangers of extracting huge quantities of wildlife from ocean systems, many nations are gearing up to go after the last three remaining large aggregations of wild protein on the planet: Antarctic krill, open ocean squid and certain deep-sea organisms. The connections between krill and an entire suite of Antarctic wildlife are well established, but few people appreciate that the tiny crustaceans are part of a complex system that also supports humankind. Extracting millions of tons of squid from the open sea has already affected albatrosses, fish, seals and others who depend on these ancient mollusks for sustenance. And while some question the wisdom of exploiting wildlife in the deep sea before we have explored that realm, others are using current freedom-of-the-seas policies to make fish meal from huge numbers of nameless small fish that glow in the dark water, mysterious shrimp with great black eyes, translucent jellies and other elements of some of earth's oldest habitats.

More has been learned about the nature of the seas in the last half-century than during all preceding history, and a few measures have at last been put into place to take care of the natural systems that fundamentally take care of us. Some 1,200 protected zones have been established in coastal regions worldwide. While the area involved is less than .1% of the oceans, nothing at all was safeguarded 25 years ago. Cultivating species adaptable for farming and acceptable to our palates is a promising alternative to capturing wildlife in commercial quantities. There are good reasons to think that in 1998, declared the Year of the Oceans by the United Nations, people will focus on aquaculture and other ways to balance ocean use and ocean care.

Perhaps, after all, those skeptical about the perils of pollution and overfishing are right, and maybe no matter what we do, or don't do, the deep and dark blue ocean will roll on. If they're wrong, we may find it hard to locate another planet with just the right kind of ocean, ready and waiting, to make life possible for us.

Marine biologist Sylvia A. Earle holds a world record for the greatest depth--1,000 m--ever reached by a solo untethered diver.