You would probably expect a pirate fort to be next to the water. Use blue plates to make water. I added a gray piece to start the shore line. You will want to use gray sloped pieces for a rocky shoreline. You can use small sloped green pieces on the shore for added detail.
To add another layer to the shore line use any color bricks behind the first layer and lay the second layer on top on them.
If your shoreline doesn't cover the whole width of your base plate, you need to add detail to the sides of the model. Here is the right side.
Here is the left side.
You have now made an awkward semicircle. Place two, two brick high pillars of any color to support the base plate that will lay above them.
Use a green base plate for the ground that the fort will sit on.
If your base plate doesn't cover the entire space, then use a few smaller plates to fill it in.
Next, take a 1x1 circle plate and place a 1x1x6 on top of it.
Next attach a ladder to a basket using a 1x2 clip.
Attach the pillar to the ground leaving room for the main fort.
Add two large arch pieces leaving four studs between them.
Add a six by six platform on top of the arches.
Add chests, buckets, stools, and hang up the ladder.
Add a small dock if you have room.
Now you can add the treasure. Add gold, jewels, guns, and anything else you think a pirate might have.
And now you a small little pirate fort.
What would you do to modify the fort and in what setting would it be?