When you find this cache you are probably also going to see a beautiful sunset. Try to be here around 5.30 PM for the sunset! Be careful there is often a lot of mugglers on this spot :-)
You can access the cache by walking on the beach. There is also a road 30 m up where you can go by motorbike or car. If you walk from Serendipity it will take you about one hour to Otres beach, remember to bring a lot of water!