This is just a wild guess (can't test atm) but you might need to add the position0 attribute to the seaparticle. Open up the attribute editor for seaparticle and under the per particle array section there is a add dynamic attributes or something like that. Anyway, hit the button that says General and from the particles tab choose position0 (or was it pos0)... Again this came from my very tired memory... I'm off to sleep now