The world's smallest marine mammal -- the critically endangered vaquita porpoise, which lives only in Mexico's Sea of Cortez -- is believed to have only 10 living members, if that, of the species. The vaquita is widely thought to be on the verge of extinction, but a new scientific analysis by a team of biologists concludes the species remains relatively healthy and can survive -- if the illegal use of 'gillnet' fishing ceases promptly.