hey scouse mike,
if you're looking to dive in cuba, it might be worth taking a look at:
www.surfacewatch.com/divesites/caribbean/cuba.html
If you are going in January/Feb, then you're probably looking at a water temp of between 23c - 25c. In terms of the visibility, that'll depend on the dive site(s) you dive at.
There are plenty of dive centres and tour operators around Cuba, the people are very friendly but some of the scuba equipment is a little dated so make sure you check it out before hiring kit.
If you want any other info, just let us know!
All the best
Claude - Surface Watch