I admit, I kinda just use whatever word pops to mind first when it comes to bodies of water I can't see the other side of. And growing up for a formative several years in Texas, lots of bodies of water become gulfs (thanks to the Gulf of Mexico). I figure this is why I'm not the geography major in my family. That, and my insistence on archipelagos and fjords featuring heavily into any map I make regardless of geographic probability.