To start, this is definitely my favorite spot in TCI. It's absolutely beautiful and secluded. Many reviews talk about the route there, which adds to the adventure. I've included some photos to help you decide if you want to drive there.
In February 2018, we drove to Pirate's Cove in a small rental car (see photo). Head northwest on Millennium Highway and turn left onto Lighthouse Road. This is the long road that goes all the way southwest. Just follow it down. Some parts of the road are a bit rough (again, check out the photos). The road is paved for a while from Millennium, but once the pavement ends, it took us about 30 minutes of careful driving to reach the beach. The worst part is from this point until the road that connects to the airport. The most challenging part is right before the airport road. After that, it's a smooth drive on a mostly flat, sandy road.
When you get there, you might see on Google Maps a spot called "Bonefish Nude Beach". While technically it could be (a tour guide mentioned that some people use it that way), it's more of a quiet, secluded beach. I didn't see anyone in the nude. To the left, you'll find Pirate's Cove and Split Rock...