Coco beach is a fair walk north from the ferry dock, tho a nice and doable walk. We stayed in a lovely condo complex in that area so the beach was only a few minutes walk away.
If you do a google satellite view Coco beach is where all the small fishing boats are anchored north of downtown Playa. There's also a nice beach bar/restaurant there with free chairs out onto the beach if you do drinks/lunch.

Hidden Beach resort does allow day visits, $100 per person, and you have to call and arrange in advance to be let thru the gate. We went up a few times, first with friends, and then took the mini-bus from Playa. If I recall earliest in is around 9 am and you have to be out by 5 or so. The resort is a bit of a walk from the main road unless you can catch one of the small resort shuttle carts.