Go right on the beach and there is a dock. Or click on the map location where the moll is it will let you access it too. Or use small circle on the top next to map to the rightest.
It is unlocked by playing until you visit Amy and Natalie outside somewhere, or you can use content skip and jump to beach immediately too. Make sure you read random meetups on the right under tasklist when they appear, it can unlock through that third option too after being in 15+ game day.
