Our earth is sustained in an endlessly rocking cradle of water. From Prince Henry the Navigator of Portugal in the 15th century to Christopher Columbus, Ferdinand Magellan, and Captain Cook, early explorers had a hint of this startling fact. Modern scientists and environmentalists also are aware of our dependence on the one world ocean.
But not until the Apollo astronauts did mankind truly see its water planet for the first time. We saw ''home'' as a bright orb mantled in blue and framed by the black of space. Brown and green continents, partly concealed by lovely cloud patterns of white water-vapor, turned as islands.
The view transmitted by America's pioneering star-sailors affirmed there is no separation between the earth's destiny and that of the sea.
We peer out from island masses. With 70 percent of the globe covered by water the continents need to be understood as patches of land in the ocean. And not, as in the past, as dominant land masses surrounded by water. The ''difference'' sounds subtle, but is actually enormous.
To understand ourselves we must understand the waters of the world. Our schools must teach this. The challenge for educators is immense.
No longer can students be timid bathers on the shores of global thought. They need to get their feet wet in more than disparate and haphazard marine-biology curricula. They must plunge into the full spectrum of the oceanic frontier if a common sense response to its potential is to affect their lives.
And like the tides that guided the first explorers' sailing ships, a number of contemporary currents are charting the course for more direct involvement by schools in oceanic education. They include:
* A broad-based environmental awareness of the delicate balance of the coastalzone and the creative tension of competing claims made on it: by land developers, the fishing industry, and ''sea-creation'' (boating and maritime leisure pursuits.)
* Maturing of the 13-year-old National Oceanic and Atmospheric Administration's (NOAA) Sea Grant program, which seeks to do for marine research and education what the land grant colleges have done for agriculture.
* Awareness of the Law of the Sea Conference and the international consensus it is trying to hammer out - a first in the history of man.
* The technological leadership of the United States in oceanography, offshore oil drilling, and deep-sea bed mining at a time when the US is looking to be more competitive in world commerce.
For Dr. John Bern, director of (NOAA), ''The seas can no longer be looked at as barriers. They must be seen as links; and the Law of the Sea conference is a clear example of this.
''Any time you can get 160 nations together to talk about common law it is very positive for the development of mankind. This positive side of increased ocean understanding is what must be communicated to students,'' he says.
Yet in talking with marine educators one barrier becomes clear: Ocean-related education has resided too long in the ivory towers of graduate schools of oceanography, naval and merchant marine academies, or institutes of naval architecture. The tide must change, and ocean education must come ashore not only in undergraduate programs, but in elementary and secondary schools as well.
''The problem of oceanic education transcends the interest of the marine science community, the environmentalists, the oceanic technician. What we must deal with is the understanding of the American people at all levels,'' says Gilvin M. Slonim, president of The Oceanic Education Foundation.
With the television his classroom and countless viewers his students, one teacher who most links the 20th century to the watery world of Neptune is Jacques Cousteau.
''We are concerned about education, about what the ocean really means. And not only for resources, but for life - for quality life, which is what we have to assume,'' Cousteau says.
Gazing out the 32nd floor window of the Cousteau Society's island headquarters in Manhattan, Captain Cousteau says, ''The goal of education is really to show the children there is something else than concrete in life. That they have to fall in love with these things in order to protect them and keep them as an asset, an incomparable asset. To own it, and to extend the scope of their life.''
But there exists a tension between the specialist and generalist in oceanic education.
The trickle-down knowledge from specialized marine-research schools needs to take into account the fact that this country was ''discovered'' by sea; its forbears came here in ships; the clipper ship was invented here; in World War II the greatest Navy and merchant fleet of all time was built here; that Herman Melville wrote ''Moby Dick;'' Richard Henry Dana produced ''Two Years Before the Mast;'' Ernest Hemingway told the tale of ''The Old Man and the Sea;'' and Anne Morrow Lindbergh gave us ''Gift from the Sea.''
DSEA:Even our maps are all wrong when it comes to understanding our water planet.
''You must think in contour maps when discussing the sea - multilevel, multinational and multidisciplinary,'' says Mr. Slonim. ''World geography is ocean geography.
''Despite 200 years of dependence upon the sea, the United States to date has failed to provide education pertaining to the seas within American schools,'' he continues. ''At the water's edge an entirely new world of human enrichment, human enjoyment, of oceanic thought and action, of challenges to the mettle and spirit of men and women emerges.
''The most critical element which has been lacking insofar as seeking oceanic and global understanding by American citizens has been teachers who are trained, educated, motivated, and confident in their teaching of the full spectrum of disciplines to the world ocean, humanities as well as sciences,'' Mr. Slonim concludes.
This is not to say that institutions like Woods Hole Oceanagraphic Institute on Cape Cod in Massachusetts, or Scrippps Institution of Oceanography in La Jolla, Calif., aren't important. They are the cutting edge of new research about the ocean deep: biology, chemistry, geology and geophysics, ocean engineeering, and physical oceanography.
But the kind of student and curriculum these graduate schools serve are very specialized.
(Dr. Charles D. Hollister, dean of the graduate program at Woods Hole, offers this advice to the interested college science major: ''Take an extra year and concentrate on mathematics and physics, then apply. I can't emphasize enough that math is the language of science and without a solid foundation in math a student can't talk about what it is he or she will research about the oceans.'')
Sea Grant is a crucial link in developing a broad-understanding of the sea. It is the catalyst transferring the specialized knowledge generated at major maritime research universities to the broader public. This is done at the local level much as the county agent in agricultural extension programs.
In the last five years, in addition to its support of research and marine resource development, Sea Grant has begun to develop a marine environment education program. A spokesman states, ''Sea Grant people are not going to be in there teaching the kids, but they will be helping those who are.'' Sea Grant has set its sights on having at least one institutional marine education program in each of the 30 coastal states. Coastal states include the eight Great Lakes states as well as those directly bordering on the oceans. When inland waterways that give access to the oceans are taken into account, there are 40 coastal states.
An interesting sidelight to these classifications is that the state with the highest per capita boat ownership is the desert state of Arizona.
Uncertainty over budget cuts has caused concern among Sea Grant personnel. The Reagan administration's David Stockman, chief of the Office of Management and Budget, called for elimination of Sea Grant's $31 million budget. The House appropriated $21 million and the Senate $41 million. The issue now is before a joint conference committee.
Even with education about the oceans for everyone relatively new, there are still numerous marine studies programs in schools throughout the country.
Big city school systems, despite budget cutbacks, still have the resources to offer some students enhanced marine education curriculum.
Los Angeles County Public Schools offer a unique opportunity to study the marine environment aboard a marine science floating laboratory. Beach Channel High School, a magnet school in New York City, centers its entire curricula on oceanographic subjects from literature to the sciences. The Oceanic Studies program at McLean (Va.) High School began its seventh year this fall.
Classroom outings to coastal areas and whale watches along both the east and west coasts are some of the more popular field trips.
Speaking as a specialist, Dr. David Ross, director of Marine Policy and Ocean Management at Woods Hole asks: ''Imgaine 100 oceanographers in a country like Somalia. Compare the contribution they could make to the standard of living of the people there as compared to 100 physicists, or 100 military advisers? The coastal fisheries could be studied for the greatest return of protein. Harbor, housing, or mineral (oil) development could move forward. The possibilities are unlimited.
''Then imagine these 100 oceanographers in each of the countries throughout the third world. The transfer of technical skills would just be the beginning, the world could be changed,'' he emphasizes.
As a generalist Jacques Cousteau promises that love of knowledge about the seas will generate its own intellectual passion. ''Learning provides extension - extension by knowledge, by sharing, by love, and by creation.
''We cannot find happiness in contemplating ourselves; but we can find it in contemplating infinity. Reaching out, with our imagination, toward its majesty, it will in turn embrace us and inspire us.
''For students, the sea is big enough for both the specialist and the generalist.