SEA OF CORTEZ, MEXICO » Snorkeling and beachcombing in the Sea of Cortez is like taking a trip to another planet. Last week, in one hour in the corner of one little cove, I saw a bull's-eye stingray, some blue-and-white jellyfish, red sally lightfoot crabs, two king angelfish, an orange fish unknown to me, collector urchins the size of cantaloupes, an intact snake skeleton, an osprey nest in a towering cactus and at least 10 kinds of seabirds. Oh, and the whole time I walked and swam, a bunch of vultures circled overhead hoping I'd drop dead.

The out-of-this-world feeling I get here comes from the stark contrast between land and sea. Here the desert rises up in jagged mountains that plunge directly into a strip of water teeming with life.

Wide temperature changes in the air and water are responsible for this abundant marine life. Summer air temperatures here are in the 100s, and the water temp rises to 85. In the winter, both air and water drop as low as 60 degrees.

Because cold water is heavier than warm water, it sinks, pushing up nutrients (dead things) from the depths. Cold water also holds more oxygen, and that, combined with the nutrient turnover, makes the water well stocked with staples.

“;I once counted 26 pods of dolphins when I sailed across,”; a retired biologist told me. “;Imagine the biomass in that water that can support so many dolphins.”;

You don't have to imagine it. You can see it on the surface, at the edges and in the markets. This sea hosts 900 species of fish, colonies of sea lions, seabirds galore and the widest variety of whales and dolphins found anywhere on earth.

Then there's the desert, also full of fantastic wildlife, but on the opposite end of the water scale.

Since I've been here I've seen two scorpions, the snake skeleton mentioned above and a large lizard skeleton. I find these treasured remains during my beach walks. Crabs and ants pick the bones clean, and the desert sun bleaches and preserves them. Dried-out ligaments hold the skeletons together like tiny leather laces.

Along the shore, cactuses of every shape, size and color thrive. The tallest are called cardons, growing up to 60 feet tall.

These resemble the saguaro cactuses of the American Southwest, except cardons have fewer elbows in their sky-pointing arms.

Ospreys like to make their enormous nests in the crook of these prickly arms.

My favorite desert animals (so far) are the turkey vultures, named for their red, wrinkled, featherless heads. They're so ugly they're cute. These crackerjack recyclers fly everywhere checking out the slightest movement, but they don't like the water. When a dead manta ray washed onto a half-sunk dinghy, gulls feasted while the vultures watched frustrated from the shoreline.

One time, while driving a rental car on a desert road around a bay, so many vultures circled overhead, I stopped to see what they were up to. But when I got out of the car and looked up, I couldn't believe my eyes. The big black birds were frigate birds riding the desert winds.

On maps this body of water is called the Gulf of California, but John Steinbeck preferred its former name, calling the Sea of Cortez “;a more exciting name.”;

And exciting it is. Sailing the Sea of Cortez is like taking a voyage to the twilight zone.