Shoals of fish abound in Puerto Vallarta ’s waters. Four billfish species are found in deep-sea grounds several miles offshore: swordfish, sailfish, and blue and black marlin. All are spirited fighters, though the sailfish and marlin are generally the toughest to bring in. The blue marlin is the biggest of the four; in the past, 10-foot (3-m) specimens weighing more than 1,000 pounds (450 kg) were brought in at Pacific-coast marinas. Lately, four feet (1.2 m) and 200 pounds (90 kg) for a marlin and 100 pounds (45 kg) for a sailfish are more typical. Progressive captains now encourage victorious anglers to return these magnificent “tigers of the sea” (especially the sinewy sailfish and blue marlin, which make for poor eating) to the deep after they’ve won the battle.
Billfish are not the only prizes of the sea, however. Serious fish lovers also seek varieties of tuna-like jack, such as yellowtail, Pacific amberjack, pompano, jack crevalle, and the tenacious roosterfish, named for the “comb” atop its head. These, and the yellowfin tuna, mackerel, and dorado (which Hawaiians call mahimahi), are among the delicacies sought in Puerto Vallarta waters.
Accessible from small boats offshore and by casting from shoreline rocks are varieties of snapper (huachinango, pargo) and sea bass (cabrilla). Closer to shore, croaker, mullet, and jewfish can be found foraging along sandy bottoms and in rocky crevices.
Sharks and rays inhabit nearly all depths, with smaller fry venturing into beach shallows and lagoons. Huge Pacific manta rays appear to be frolicking, their great wings flapping like birds, not far off Puerto Vallarta shores. Just beyond the waves, local fisherfolk bring in hammerhead, thresher, and leopard sharks.
Also common is the stingray, which can inflict a painful wound with its barbed tail. Experienced swimmers and waders avoid injury by both shuffling (rather than stepping) and watching their feet in shallow waters with sandy bottoms.
Although seen in much greater numbers in Baja California’s colder waters, fur-bearing species, such as seals and sea lions, do occasionally hunt in the tropical waters and bask on the sands of island beaches off the Puerto Vallarta  coast. With the rigid government protections that have been enforced for a generation, their numbers appear to be increasing.
The California Gulf porpoise—delfín or vaquita (little cow)—once very numerous, is now rare. The smallest member of the whale family, it rarely exceeds five feet (1.5 m). Hopefully, if conservation plans are successful, its playful diving and jumping antics will again be observable from Puerto Vallarta–based tour and fishing boats.
Although the California gray whale has a migration pattern extending only to the southern tip of Baja California, occasional pods stray farther south, where deep-sea fishermen and cruise- and tour-boat passengers see them in deep waters offshore.
Larger whale (ballena) species, such as the humpback and blue whale, appear to enjoy tropical waters even more, ranging the north Pacific tropics from Puerto Vallarta west to Hawaii and beyond.
Offshore islands, such as the nearby Marietas and María Isabel (accessible from San Blas), and the Revillagigedo (ray-vee-yah-hee-HAY-doh) 300 miles (480 km) due west of Puerto Vallarta, offer prime viewing grounds for Mexico’s aquatic fauna.