Some of our favourite beaches in Croatia are in Dubrovnik, and if you are visiting for the swimming and the coast then you will love it! The best beaches in Dubrovnik in our opinion are Sveti Jakov Beach, Banje Beach, Šulić Beach, Bellevue Beach, Lapad Beach, Copacabana Beach and Coral Beach Club. Buza Beach is another area to swim, and if you visit Lokrom Island you can swim here too either at the rocky beach area, or other pretty spots around the island.
If you are after more details you can take a look at our article on our blog: https://almostlanding.com/best-beaches-in-dubrovnik-croatia/