The Caribbean monk seal was a relatively small seal, the upper parts nearly uniform brown, tinged with gray; sides paler; under parts pale yellow or yellowish white; soles and palms naked; pelage very short and stiff; nails on anterior digits well developed, on posterior digits rudimentary. Very little scientific information was gathered before the Caribbean monk seal disappeared. Males are thought to have reached a length of 2,1 to 2,4 meters, females may have been slightly smaller. The fur of newborns was long and dark. Evidence suggests that the pups were born in December weighing between 16 and 18 kg, and measuring up to 1m in length. All monk seals rest and give birth on sandy coasts, on remote islands or undisturbed beaches of the mainland
Now extinct, the Caribbean monk seal was the only seal native to the Gulf of Mexico. They were tropically distributed but limited to the Gulf of Mexico coast, Yucatan Peninsula, western Caribbean Sea, the Greater and Lesser Antilles, the Bahamas, and the Florida Keys. Records from Texas include one sighting in 1932 and several instances of remains recovered from coastal archaeological sites. M. tropicalis probably became extinct by the mid-1950ís.
All monk seal species appear to be sensitive to disturbance, and early habitat exclusion by humans throughout their range may have exacerbated their decline. The end of the 19th century witnessed relentless slaughters and the species had already become rare in the 1880's, before it was properly known to science.
H. Sloan wrote in 1707: "The Bahama Islands are filled with seals; sometimes fishers will catch one hundred in a night". The Caribbean monk seal was documented as being easily approachable and not aggressive. They were easily killed during directed hunts in the 17th and 18th centuries. It is also known that sailors, whalers, and fishers opportunistically killed the seals they encountered. As well, Caribbean monk seals were killed by museum collectors and displayed in zoos.