I've gotta say this is one of the cutest shower ideas that I have seen in a while! The inspiration board above was designed by Erika Ward from Blue Label Bungalow. Just look at the adorable cupcakes with alternating shark fins in water and sand with the umbrellas! Some with white icing and little boats on top in orange would be adorable too! For the table setting, I would put the fish netting over marine blue and kelly green table cloths and tie white napkins with mini grosgrain belts similar to the ones shown above. Additional cute centerpieces would be ships or green and blue beach toys resting in sand.
Some good websites for purchasing personalized melamine plates for the honoree similar to the ones above are La Plates & My Clean Plate Club. These make great gifts for any occasion.