I have a Mares 3mm full that I've been using for diving. Any ideas if it will be okay for windsurfing? It's a bit on the tight side, which is fine for diving as it expands but not so sure for out of water stuff.
If not, what would be a good alternative for 13oC water (Spanish winter)?

It'll work but won't be ideal as it won't be nearly as flexible as a windsurfing suit.

As far as alternatives go then any suit made for windsurfing, kitesurfing or surfing will be fine and something 3mm will probably be ideal for 13¬?C water.

Al.

I agree, diving suits never work very well for windsurfing because they are very thick & restrict movement. This is fine for slow moving diving but for windsurfing it will cramp up your arms & make everything you do seem extra hard work!

I would recommend any of the big names in wetsuits: Billabong, O'neill, Ripcurl, etc

You can see the Billabong wetsuits we use at the Poole Windsurfing school on this page:
http://www.poolewindsurfing.co.uk/billabong-foil-wetsuit/

They all make extremely good wetsuits that feel incredibly flexible when you put them on! In terms of thickness you could go for a top of the range 3/2mm wetsuit with taped & glued seams so that no water can get in. A top of the range wetsuit like this will mean you can stay in a 3/2mm thickness for much longer into the oddslot winter months but there will come a time (& temperature) when a 3/2mm just won't do it anymore. For the really cold months you will feel a big difference if you get a 5/3mm winter wetsuit & now a days they are still very flexible & light weight.

Hope this helps you get started on your search for a nice new wetsuit.

Happy windsurfing!

[Edited on 13-3-2011 by Poole Windsurfing]

You can use diving suits for windsurfing without worries. If you have a thinner one without sleeves it is great. If you would like to know more about this sport check this windsurfing site... It provides gear reviews, tutorials, destinations and more.