In Nancy Drew: Sea of Darkness, you can find up to 4 Easter Eggs in the game.
The first is to open the triangle button box in the Captain’s Quarters BEFORE you solve it for real. Your goal is to get the three darker yellow triangles pressed down. If you number the triangles from left to right, top to bottom, press them in this order: 2-6-5-8-6-9-7. If you open the box to get the papers first, you will no longer have the opportunity to get the egg.
The second egg is in the pub. When you step into the kitchen to fill food orders, fill all the trays with puffin. If you don’t have the option of puffin, back out of the kitchen and return until you do. Once the trays are filled with puffins, you will here a chicken cluck. This means the egg is now available to find in the seating area of the pub. Leave the kitchen and go up to the stage. Look to the left and find the egg resting on the cello.
The third egg is in the wheelhouse. After you learn the trick to distract Elisabet, step up to the chair and open and close the flap on the arm for the emergency alarm. Click on the button (and hit your back-up button, to close it) until you get an egg.
The fourth egg is the hardest to find. Step into the ice caves with your flashlight and follow the path until you reach the very first junction. Look for the yellow pumice stone on the left wall that is protruding just barely out of sight. Turn left towards it. Continue onward to the end of the tunnel and use your fish hook on the small mound of ice in front of the ice wall. The Easter egg hidden here was made by a football fan. Blue and lime green are the Seahawks colors, the XII represents the number for the fans “The 12th Man,” and the tiny numbers on the upper and lower rims represent the players who were involved in the 2014 Super Bowl.
To use any of your Easter eggs: you can make a purchase at the gift shop for ANYTHING for free – except for the sword. (You’ll have to earn that on your own.)