I like the aderondack on the beach. What can you do with a lighthouse concept that presents the idea of a beacon that protects a boat from crashing on the rocky shores? Like a beacon of light guiding you on your journey?
Also, can you do a coast landscape thing? Check out the work by Mary Helmreich as an example at: :
http://fineartamerica.com/art/paintings/north+county+san+diego/all