In addition, swells can be developed in the open ocean by surprisingly distance storm systems.. these can roll into the otherwise 'leeward' sides of islands.
Having snorkeled in Mexico and Tahiti I certainly prefer the islands with a barrier reef. The waves in Mexico - exposed on the Pacific side with a red flag warning the whole time I was there - were awesome. There was a storm 'at sea' according to the locals; but 150 yards off shore the waves were barely noticeable on our boogie boards. Move in closer to where the breakers formed and it looked like some kind of life and death struggle!