This would be a marine veterinarian or an aquatic veterinarian.
General?
Vetrinary
A doctor who specializes in the care of animals is called a Veterinarian.
Someone who takes care of animals would be a Veterinarian. It could also be a farmer, or a zoologist. Even an animal trainer.
a vet
The same as you would call a Male doctor. a doctor!!!
A marine veterinarian or an aquatic veterinarian.
that doctor is an ORL (oto-rhino-laryngologiste)
You should call someone who takes care of animals like Animal Control or something.
I would call them an aspiring veterinary nurse or an aspiring veterinary surgeon.
It is also called a doctor, but there can be different types such as psychiatrists, pediatricians and surgeons. However, if not human, you can visit the vets , which cure all animals.