Tami - I'm a diver and a former chemist too. Here's a few things about neoprene:

- blown foam neoprene ala wetsuits does absorb some moisture; solid neoprene ala mechanical seals does not do so nearly so quickly. This has much less to do with the chemical structure of neoprene, than the construction of the material.

- sweaters work the same way as wetsuits do - air can get through your sweater, but the sweater traps a layer of air you've warmed with your body heat as an insulative layer. Air is not as conductive as other things. Although sweaters work to keep you warm (just wear one on a sunny day), you notice that cold air does still get through (why you still need a windbreaker on a chilly windy day). Neoprene wetsuits aren't nearly so permeable, but they are still permeable. This is less a physical property of the compounds in question than a mechanical property of their assembly.

- wetsuits do have pockets of air trapped in the foam 'matrix' - that accounts for bouyancy - but some water does get in through there. As Matt the Hobie guy says, a mast full of mostly air is more bouyant - that's because that air amounts to a giant air pocket/bubble, instead of lots of tiny ones.

Water molecules are rather small, just like, say, diatomic helium (think balloons), and they are capable of getting through very small "holes" in the 'matrix' of most solid compounds. You will notice that a helium balloon loses gas slowly, over a couple of days. That's because there are lots of very tiny holes - spaces between the rubber molecules - in the rubber of the balloon - and the gas leaks out very slowly through those holes, but it does.

Similarly, in neoprene foam, there are lots of tiny "faults" and voids in the neoprene, in addition to the air pockets. Water makes it's way in there. I think it's likely that neoprene that spends it's time at the top of a mast 99.9% of the time would stay pretty dry. But, Polystyrene (good old foam cooler material) foam is probably lower density. That stuff is also water-permiable, BTW. IIRC, the only mast float I've ever seen, on an Aqua-Cat, had a plastic skin around a polystyrene core - the skin helped provide mechanical protection, while the core provided bouyancy.

Finally - that's a great avatar.