✨ Sea You Real Soon: Castaway Cay

🪸A Dredged Channel on a Carbonate Platform

Welcome ashore… without stepping ashore.

As you approach Disney's Castaway Cay, you’re visiting an island shaped not only by imagination, but by geology. While many explorers arrive aboard a Disney cruise ship, this EarthCache can be completed from any vessel in the surrounding navigable waters.

Castaway Cay sits atop the Bahamian carbonate platform — a vast, shallow underwater bank composed primarily of calcium carbonate (CaCO₃) produced by marine organisms. Over thousands of years, corals, shellfish, algae, and microscopic organisms created calcium carbonate skeletons. When they died, their skeletal remains accumulated on the seafloor, compacted, and hardened into limestone.

Carbonate platforms form in warm, shallow tropical seas. Unlike volcanic islands, which rise steeply from deep ocean water, carbonate banks are broad and shallow.

One of the clearest pieces of evidence for this shallow platform is visible today: the dredged ship channel leading to the dock.

Large vessels cannot naturally approach the island because the surrounding seafloor is too shallow. To allow docking, a deep-water channel was excavated through the carbonate sediment and limestone layer.

This EarthCache explores how human modification of the seafloor reveals the natural geology beneath. By observing the dredged channel and comparing it to the surrounding shallow water, visitors can see direct evidence that Castaway Cay sits on a shallow carbonate platform.

🌊 What You Can Observe From Offshore

This EarthCache can be completed from any vessel in navigable waters near the island.

From the water, observe the dredged channel leading toward the dock. Notice the contrast between:

• The deeper, darker channel

• The surrounding shallow, bright turquoise water

The turquoise color indicates shallow water over light-colored carbonate sediment. The darker channel indicates increased depth where material has been removed.

At Castaway Cay, geology quite literally shaped where ships can and cannot sail.

🧭 Logging Requirements

To earn your smiley, email the answers to the following:

1️⃣ Observe the dredged ship channel. Describe how its water color and depth appearance differ from the surrounding shallow water.

2️⃣ Estimate how much deeper the channel appears compared to the surrounding water (for example: slightly deeper, twice as deep, significantly deeper). What does this suggest about the natural depth of the carbonate platform before dredging?

3️⃣ Based on your observations, explain how the need for dredging provides evidence that the surrounding seafloor is naturally shallow carbonate sediment rather than a steep volcanic island.

📸 Required Photograph

Include a photo in your log showing the offshore view of Castaway Cay from your vessel, with the island visible in the background.

You (or a personal geocaching item) must appear in the photo, or your vessel must be clearly identifiable in the image.

This photo should reflect your on-site observation and connection to the location described in this EarthCache.

Sea you real soon! 🪸🌊🚢