Where can you find the world’s largest whale and a tiny nudibranch in one week of diving? The Gulf of California, also known as the Sea of Cortez, hosts an incredibly abundant and rich marine biodiversity in some 68,000 square miles of water. It offers a unique opportunity to encounter many migratory species like humpback whales, California gray whales, killer whales, manta rays, Humboldt squid, sea turtles and the world’s largest animal, the blue whale. There are also resident populations of fin and sperm whales, sea lion colonies, whale sharks that gather in Bahia de los Angeles to feed, more than 900 varieties of fish, and thousands of micro-invertebrates.

One of the best ways to explore the Midriff Islands — a group of more than 50 islands scattered over 80 miles in the north-central gulf — is aboard Rocio del Mar, a 110-foot liveaboard that can host up to 20 divers in comfortable air-conditioned cabins. The boat will be your home away from home, with its spacious salon, dining area, dive deck with plenty of space for camera gear, a sun deck and lounge area. Best of all, experienced, local dive guides will take you to the choice spots.

The Midriffs — or Islas Grandes — are separated from the Baja California Peninsula by the Canal de Ballenas (Whales Channel). Many of the dives take place off Isla Angel de la Guarda. At sites like Andrea’s Eagle, you’ll encounter an amazing sargasso forest sheltering blue-spotted jawfish and orange-throat pikeblennies, darting in and out of their burrows.

The sites La Vela and La Muela are teeming with macro life, and you’ll have your first of many encounters with California sea lions.

One of the highlights of this trip is a snorkel-only experience that takes place at Bahia de los Angeles, a coastal bay on the eastern shore of Baja California, where dozens of whale sharks gather near the surface to feast on the abundance of plankton. The Sea of Cortez is often called the Aquarium of the World, and after one week of diving there, it’ll be easy to see why.

TRIP HIGHLIGHTS

Day 1

Rocio del Mar departs Puerto Peñasco at 6 p.m. You’ll wake up the next day with dive sites awaiting at Refugio Bay, off Angel de la Guarda, about 125 miles from Puerto Peñasco.

Day 3

Humboldt squid encounters — or at least sightings — can happen at night. The squid, along with other nocturnal hunters, are probably attracted to Rocio del Mar’s powerful lights.

Day 5

Once the boat has moved to San Pedro Martir, you’ll likely get to dive with sea lions; the pups are especially curious and will come close, even tugging on your fins.

Day 7

On your way back to Puerto Peñasco, snor- kel with whale sharks in Bahia de los Angeles. You can have encounters with 6-foot juveniles and huge, 20-foot adults.

THE BOAT: Rocio del Mar

Cabins/Guests: 10/20 max Total crew: 11 Length: 110 feet Number of decks: 3 Contact: rociodelmarliveaboard.com