Nothing restores excitement to diving like going eye-to-eye with animals bigger, stronger and faster than you. Just swimming with seals, sea lions and even really big fish can make you feel slow, clumsy and vulnerable. And the concept of a food chain is much less abstract when somebody else--say a six-foot blue shark--is at the top of it, and he's sizing you up.

That's why we love diving with big animals. It shakes things up, alters our perspective and sometimes, it just scares the hell out of us. No other state offers as many opportunities to swim with the big dogs as California, so we went in search of the best big animal adventures we could find.

Deep Water, Cold Fear: Open Ocean Shark Dives

• Target animals - Blue and mako sharks.
• Dives offered from - Catalina Island and San Diego.
• Recommended skill level - Intermediate to advanced.
• Adrenaline factor (1-10) -10.

Before you sign the waiver, and climb into the shark cage, there are some things you should know about the pelagic blue and mako sharks found off California.

They are truly wild and unpredictable. Unlike territorial reef sharks in the Caribbean, they roam the ocean and aren't really used to seeing divers--which adds an extra edginess to encounters.

Blue sharks, the most common species, are fairly mild-mannered for a shark with a man-eater reputation. They are rarely aggressive, and almost always approach the boat up-current, following the drifting chum to its source. They're curious, and examine new things by tasting. So when a big blue wedges its snout into the cage and bites the bars, it's probably just window-shopping, says boat operator Jay Furlin of Dive San Diego. "Puppy dogs," he calls them.

But makos are like mean junkyard dogs. They are fast and aggressive. They like to take prey from behind, and will frequently approach the boat not up the chum line but from the opposite direction, having made a wide circle. "They're hunting," says Paul "Doc" Anes, owner of San Diego Shark Diving Expeditions. "Frankly, they scare the bejeezus out of me."

Once, Anes was outside the cage, baiting the water as blues approached. He happened to look to his side and saw a flash in the corner of his eye. "Suddenly, there was a mako with his mouth open coming at me. I kicked and punched him, and he veered off." Anes was protected by his stainless-steel mesh suit, but the shark made off with one of his fins.

That's the kind of fun you can have, too. Of course, you'll be inside the cage. Most of the time.

What You'll See

Sharks, of course. Though you can't be sure. Because of commercial fishing, sharks are less common off the California coast than they once were. Anes and Furlin claim a 90 percent success rate in finding sharks. On a typical trip, you'll see five to 10 sharks, maybe 20 or more. Most will be blue sharks, in the four- to six-foot range. You may see one to three makos. On average, they're a bit smaller than the blues, in the three- to five-foot range, but the intensity level goes up when they arrive.

The Drill

1. The cage is lowered into the water and suspended 15 feet below the surface from a buoy. It's an aluminum frame with steel mesh between the bars, about eight feet high and long, four feet wide, with room for two to three divers inside. Now here's the tricky part: When the sharks are circling, you want to get from the boat to the cage as quickly as possible--for obvious reasons. No dawdling on the surface while you adjust your weight belt and put on your gloves, please.

2. The divemaster (the one in the steel chain-mail suit) will accompany divers to the cage one by one, so follow his directions. Normally, you'll enter the cage from the rear, while the sharks (usually blues) are occupied with chum in front of the cage, so there's little danger.

3. Once all divers are in the cage, the divemaster will move to the front of it and resume chumming in order to draw the sharks close to the cage. You'll spend about 30 minutes in the cage, then return to the boat so another diver can take your place. On most dive trips, you'll have time for two or three of these rotations.

Shark Diving Tips

• Be a confident, comfortable diver. Know your gear. It's important to make the transition between boat and cage quickly, without wasting time getting "settled." A shark dive is not a good choice for one of your first dives after certification.
• Add four to six pounds. Be negatively buoyant so you can stand easily on the bottom of the cage. The cage rises and dips with the swells. It's better if you don't have to hold on to the bars with your hands to keep position.
• Enter the water negative. A deflated BC and extra weights will help you get below the surface quickly. If equalizing your ears will be a problem, remember to pressurize them slightly before you hit the water and to equalize continually.
• Avoid "Yum-Yum Yellow." There's not much proof, but it's believed that bright colors, especially yellow, are attractive to sharks. Maybe even appetizing. Just in case, leave the yellow fins at home.
• Don't get seasick. Because the boat will be drifting, it will turn sideways to the swell, and it may begin rolling deeply. If you're susceptible to seasickness, begin taking medication early. In fact, it often helps to start the night before.
• Watch your step. A boat's roll can become violent. Be careful when moving across the deck. Wear booties with a good grip both to the deck and to your feet, and use handholds when you can. This is one of those occasions when there's more risk to divers on the boat than in the water.

Where Did the Sharks Go?

As recently as the early 1990s, California shark dive operators routinely saw 50 or more blue sharks on every trip, up to 12 feet in size. Today, you're lucky to see more than 10 sharks, and they'll probably be smaller than five feet.

What has happened to the sharks is commercial fishing. Once a fish almost no one would eat, today shark appears on many restaurant menus, and the international market for shark fins, skins and cartilage has been growing steadily. As a result, the price fishermen were getting for shark rose from 25 cents per pound in the 1980s to more than $2 in the 1990s. Not surprisingly, more commercial fishermen began targeting sharks.

For the first time in the planet's history, sharks have a predator they are not biologically prepared for. While fish further down the food chain may lay millions of eggs a year, most sharks give birth to as few as three or four live pups. It may take 10 years or more for a shark to reach sexual maturity. Many of them are now being caught first.

And also for the first time, sharks have found human allies, in environmental groups concerned that many species of sharks face extinction. For information, contact PADI Project AWARE (800-729-72354, ext. 439, web: www.padi.com), Ocean Wildlife Campaign (202-861-2242, 516-859-3032) or the Pelagic Shark Research Foundation (408-459-9346, web: www.pelagic.org).

Other Shark Dives

While California has the most shark diving options, it's not the only state where you can go mask-to-snout with the ocean's top predators.

• Rhode Island - The dives take place 40 miles southeast of Point Judith, R.I., where you observe Atlantic blue sharks attracted by chumming.
• North Carolina - The wreck of the Papoose off Morehead City, is home to a large school of docile sand tiger sharks. Thanks to efforts to protect sharks along the U.S. East Coast, sand tigers are also found on other large wrecks.
• South Florida - Attempts to create feeding dives for reef sharks off South Florida have been thwarted by commercial fishermen who have wiped out entire populations on some reefs. Spearfishing interests have also waged a campaign of fear and are attempting to have all shark and fish feeding dives outlawed in state waters.

Circus Maximus: The Sea Lion

• Target animals - Sea lions and harbor seals.
• Dives offered from - Catalina Island, the Greater Los Angeles area and San Diego.
• Recommended skill level - Beginner.
• Warm and fuzzy factor (1-10) - 10.

If the whole adrenaline rush of shark diving seems a little over the top, there are big animal encounters of a kinder and gentler kind--sea lions and harbor seals.

The friendly pinnipeds hang out on rocks and beaches of well-known dive sites throughout the state, and if you anchor nearby, some of them will almost always swim out to you.

Seals and sea lions are almost always playful and inquisitive. They seem to play games with you, blowing bubbles in your face, tugging at your fin, swimming fast donuts around you. Glenn Fritzler of Truth Aquatics tells of a seal that looked him in the eye, grabbed his hood with its front flippers and pulled him close, face to face.

Obviously intelligent, they sometimes mimic your behavior. Jon Hardy of Argo Diving says he often picks up a horn shark, a small bottom dweller, shows it to the other divers, then puts it back. On one occasion, a seal then started picking up horn sharks too. Furlin says a pup once followed divers up onto the swim step.

Pups are the most fun. Like all children, they are more exuberant and less dignified than adults. They will sometimes present their bellies to be scratched or rocket between your legs. Often, a gang of them will enter the water together to swim out to your boat.

Seals pup January to March, sea lions March to May. It's best to let them grow a few months so that they're adolescents before diving with them. Infants are usually accompanied by nervous and sometimes irritable mothers.

Mothers may be irritable because pupping season is also mating season. Sea lions mate almost immediately after giving birth. (Their gestation period is nine months, like humans, but they're able to delay the birth for three months so births always happen about the same time every year.)

The Drill

The dive boat will anchor near a known rookery or haul-out area. The best sites are at San Miguel Island, Santa Barbara Island, Catalina Island and North Coro-nado Island. The boat won't get too close--it's illegal--but don't worry. The sea lions or seals will come out to you.

Stay fairly shallow. Although pinnipeds can dive deep, they are air breathers and will spend most of the time near the surface. They will often lift their heads out of the water to look around.

Pinniped Diving Tips

• Don't come between mother and pup. When a bit older, pups will play alone or in groups. But when Mom is close by, keep your distance.
• Don't corner a seal or sea lion. Bites are rare, but they do have large teeth.
• Be cautious about touching. It's best to treat them like strange dogs. Don't reach out until they demonstrate a friendly mood.

Other Big Animals

The Pacific is a big ocean and there's no telling what other forms of big marine life you might encounter. Every now and then, tear your eyes away from the sharks or sea lions and scan the Big Blue for:

• Striped Marlin. This open-water billfish feeds on mackerel and tuna, as do sharks. They are common in the six- to eight-foot range and can reach 12 feet in length.
• Mola Molas. Also called ocean sunfish, they resemble poker tables on edge. Often in the three- to five-foot range, they are found in the open ocean, though sometimes approach shore to have their parasites cleaned by halfmoon perch.
• Black Sea Bass. Also called giant seabass, they were fished to near-extinction, but are now protected and making a comeback. Black sea bass can reach seven feet and 500 pounds. They are territorial, and hang out near the shore. Encounters are still rare but becoming more common.
• Whales. Gray whales are once again common, and make their northbound migration along the coast between February and July. Plankton feeders, they are not interested in chum, but their spout can be seen from a long distance. It's illegal for a boat to approach close to a gray whale, but sometimes a boat will stop in the path of a whale and put divers in the water. Pilot whales (actually a porpoise) are more approachable and Argo Diving has had some luck putting divers in the water with them.
• Porpoise. Three varieties are common off California: the "common" porpoise, the bottlenose porpoise and the Pacific white-sided porpoise. Like whales, they are often seen at a distance in the open ocean because they leap out of the water as they swim. They will often change course to investigate a boat. They may be attracted to the chum, in which case they will probably scare off the sharks.

Dive In: California's Big Animal Encounters

• Dive Season - Late spring to late fall.
• Water Temps - Low 60Fs in spring, high 60Fs to 70Fs in late summer and fall.
• Visibility - Variable. Spring plankton blooms often reduce visibility to 20 feet or less, but it can peak at 100 feet in the fall.