I use a 5mm, no hood, when I do a cave dive there, and I stay reasonably warm for even a 2-hour dive. I would be cold in a 3mm suit by itself. A hood would make a difference.
As Bogtrotter said, you can rent a 5mm suit if you don't want to pack one. They will provide lights if you don't want to pack them, either.
As Bogtrotter said, you can rent a 5mm suit if you don't want to pack one. They will provide lights if you don't want to pack them, either.