Pros who may care for playful marine mammals

VETS

They might treat dolphins or seals but aren’t marine biologists.

This clue plays on the double meaning of "care"—veterinarians (vets) professionally care for animals, while "playful marine mammals" hints at dolphins or seals, which might "play" in water. The word "pros" simply reinforces that we’re looking for a professional title. The answer is "VETS," short for veterinarians, who fit both the literal and clever sides of the clue.