wetsuit thickness in Fernando de Noronha, Brazil (and other general questions)

We are doing our open water certification in Fernando de Noronha this
coming March. Water temperature is average 25C/80F. Does anybody
have experience there? Any hints? I have read the many posts about
the Agua Claras and Atlantis operators and have seen many pros and cons
in general.

We will be renting most equipment except mask/snorkel/fins, but
thinking of getting full-length wetsuits and trying to determine
whether 3 or 5 mm would be better. We were definitely shivering in
the 80F pool in 3mm. Would appreciate it if anybody has Noronha
experience and could help us with this question.

Anything else we should 'definitely' bring? We are not yet at the
commitment stage for dive computers (winning the lottery would help on
that issue!)

Thanks.