I accidentally stumbled upon a few nautical themed projects the other day so I have rounded up a few for you here. My favourite are these crochet boats from Bunny Mummy.
These coasters from Purl Bee are based on nautical flags, you can pick flags to spell a word of your choice.
A beach hut doorstop from All About You, you could also use this design on a bag or cushion.
There are lots of nautical striped jumper patterns available, I like this one from the 1950s, the pattern is available for free here from Zilredloh.
Or you could make this 1940s swim suit!