A newly launched effort to find critically endangered vaquita marina porpoises has already spotted at least two and perhaps three of the elusive, rarely seen creatures in Mexico's Sea of Cortez.

The U.S. National Oceanic and Atmospheric Administration, which is collaborating with Mexico in an effort to count the remaining vaquitas, said Thursday that two of animals—the world's smallest porpoises—were sighted.

"Jubilation and relief," was the way the NOAA described the mood at seeing the vaquitas. Experts have estimated that fewer than 100 vaquitas survive.

The tiny porpoises "were spotted swimming in calm waters near the fishing village of San Felipe, Baja California," the NOAA said.

Mexico's Environment Department said in a statement that three vaquitas had been sighted in the voyage aboard a research vessel Thursday: one male, a female, and a third whose gender could not be determined.

Nobody is quite sure how many vaquitas remain in the Sea of Cortez, also known as the Gulf of California. It's the only place they are found.

Estimates of their population have largely been based on acoustic monitors that pick up their distinctive vocalizations.

"We knew vaquitas remained because we are hearing them, but seeing them today is a great relief," said Lorenzo Rojas Bracho, the chief Mexican scientist on the observation team.

"It truly is like finding a needle in a haystack," said Dr. Barbara Taylor, the head U.S. expert on the voyage, which started Sept. 26 and will comb the waters of the upper Gulf through Dec. 3, searching for the vaquitas with high-powered binoculars.

More acoustic detectors will also be placed in .

Mexican authorities have declared a new gillnet fishing ban in the upper Sea of Cortez in a bid to save the vaquita.

The vaquita is threatened by gillnet fishing for totoaba, a huge, heavy whose swim bladder is prized by chefs in China.