Hi rickyyoung,
welcome to the Mauritius Forum!
Yes, during this time, its definitely not to hot. But I find the sea water quite cold
but thats more the impression of a local here, in summer, the sea water in Denmark for example is way colder, really icy.
For the ones who like it really hot and humid, just like the hot tropics are, i would suggest likewise as you mentioned:
Do you happen to know of some good diving spots around the island ?