Search the following locations to find a hidden sandcastle.

Guadalcanal
There are two islands (a small one and a big one). On the big island is a beach facing toward Guadalcanal as well as two trees. Follow the beach to the left of those trees to find a mini sand castle with a shovel.

Iwo Jima
On the island closest to the carrier is a small sandcastle facing the carrier.

Wake Island
There are two small islands by the beach base. On the one to the right is a sandcastle with a Swedish flag and a yellow shovel.