Have a bonfire on the beach
Everyone heads out when the beach cools off, but those who stay are rewarded with a picnic at sunset. Sweatshirts go on, somebody drags driftwood into the circle, and everyone just talks around the fire, as humans have done for hundreds of thousands of years. You may just invent something.
Go camping, glamping, whatever’s your style
Take it several steps further by living in the woods for one complete weekend. Don’t forget the campfire-friendly eats and… something to protect them from wildlife.
And by “fishing”, we mostly mean drink a beer on a boat. Bonus points for actually catching any fish. In all seriousness, there are few things in life as relaxing as sitting on deck, waiting for a bite.
Skinny dip somewhere
Pool hopping, late-night pool party, lake, ocean, kiddy pool... wherever you have the option to jump into a body of water sans shirts, sandals, and skivvies, you should do it. Just make sure everyone’s prepared first -- nobody likes a surprise skinny dipper.