If you are diving, I would say yes. I use a 3mm shortie when I'm there between March and November. This time of year a 3 or 5mm full suit would be better. Even when I go, I do start to feel a little cold when nearing the end of the dive (even with my own 'personal padding'). A full suit would help, especially when doing repetitive dives.
If snorkeling, a shortie would keep you warmer than none at all (and I don't mean naked). You tend to lose track of time when floating and body heat does drop quite quickly as you don't use much energy.
Having said that, other people may have different opinions.