ROAM THE OCEAN'S DEPTHS, WITHOUT SCUBA GEAR.

Byline: Janet Fullwood Scripps-McClatchy Western News Service

The open ocean is a world of perpetual motion, a realm with no visible boundaries and no place to hide. Until recently, the only way humans could visit was to don wet suit and scuba gear and slide inside.

Now there's the Outer Bay, a $57 million wing that opened this spring at the Monterey Bay Aquarium.

The Outer Bay throws open a window on the liquid habitat where muscular barracuda dart, delicate jellyfish drift and tiny plankton flourish in unimaginable numbers. The permanent exhibit's galleries are the first in the world to present life in the open ocean on a grand scale.

And we're definitely talking grand. The centerpiece of the new exhibit is a 1 million-gallon tank showcasing fast-swimming animals that, due to their space requirements, have seldom been exhibited before. Visitors view them through the largest single-pane window on Earth - a 54-foot-long, 14-foot-high, 13-inch-thick slab of laminated acrylic that was fabricated on site and weighs a staggering 39 tons. As big as a full-size movie-theater screen, it allows people to feel swallowed up by the water world on the other side.

``The idea was to create an immersive experience, to communicate a sense of the vastness of the habitat,'' spokesman Ken Peterson said. ``You don't want to talk about a vast habitat and have dinky little windows looking into it.''

Since it opened 12 years ago, the Monterey Bay Aquarium has earned an international reputation for its innovative exhibits. As a showcase for the habitats and sea life of one of the world's richest marine regions, it features more than 100 exhibits and galleries and attracts some 1.6 million visitors each year.

The opening of the Outer Bay, which focuses on life in the top 300 feet or so of the region where Monterey Bay meets the open ocean, 60 to 100 miles outside the aquarium's windows, marks the facility's first major expansion. A companion exhibit, the Deep, also will be housed in the new wing. Scheduled to open by the turn of the century, it will showcase life in the deepest, darkest crevasses of Monterey Bay.

The scientific and technological challenges presented by the Outer Bay project took more than seven years to resolve. The answers are still coming in - along with more questions - as teams of scientists and designers continue to observe and experiment with the exhibits.

The million-gallon centerpiece exhibit proved especially problematic. Designers wanted to create for viewers the illusion of a boundless, blue, sun-dappled habitat - one without corners or walls. This being California, the enclosure would have to be earthquake-proof as well as aesthetically pleasing.

The solution was to build an egg-shaped, reinforced fiberglass shell inside a rectangular concrete tank 18 inches thick. Water between the two structures helps support the weight of the water contained by the shell; blue liner tiles and carefully orchestrated lighting create the desired visual effects.

The aquarium's marine biologists, in selecting creatures to display in the 90-foot-long, 35-foot-deep enclosure, had to consider, among other things, which species could live together without harming themselves or each other. The elaborate collection and acclimatization processes took months - and produced some unfortunate surprises.

Several yellowfin tuna, for example, rammed themselves to death against the viewing window, unable to interpret it as a boundary. A blue-fin shark, intended as one of the exhibit's showstoppers, had to be euthanized after it failed to respond to antibiotics used to treat an infection. And a school of pelagic stingrays was removed after the animals were discovered nibbling on the fins of the ocean sunfish.

``The Outer Bay is still very much a work in progress,'' Peterson said, explaining how designers continue to ``tweak'' the lighting inside and outside the exhibit to find the delicate balance that will show off the fish to their best advantage and help them steer clear of the glass. Experiments with sea life continue, also.

``We don't know at this point how many species we eventually will have - it depends on how many the collectors can catch and keep, and whether or not they are compatible,'' said Peterson.

``For the time being,'' he added, ``we're not going to put any more sharks in.''

The aquatic menagerie in residence nevertheless is impressive. Swimming around in the tank are streamlined yellowfin tuna, menacing California barracuda, silvery bonito, a lone green sea turtle and five ocean sunfish, which can grow to 10 feet high and surpass 2,000 pounds. With their stunted tail fins, these crowd-pleasing creatures, now at about 60 pounds, look like nothing so much as swimming heads.

Other exhibits in the Outer Bay are equally mesmerizing.

In a rotunda, 3,000 anchovies swirl like liquid silver in an overhead, merry-go-round shaped tank. The next exhibits, side-by-side displays of fast-moving mackerel and undulating, purple-striped jellies, introduce viewers to the two main life forms - swimmers and drifters - that inhabit the open ocean.

``The whole thing was done with a deliberately different feeling, the intent being to create a sensory experience, to have reference points throughout the building that seem to imply the open ocean,'' Peterson said. ``It's all designed so you have no way of telling where the boundaries are.''