Gold Beneth the sea

The solution to the game is as follows:

the 4 riddle answers are: Jolly Roger, Eye Patch, Blackbeard, and Treasure map. The dashes under each one give a clue to how many letters the answer has.

To open the Chest, you need a specific letter from each word. The Location of the X is a clue for the order in which to put the letters. Where the X is is the clue  in which order you must put the letter. The X in eye patch is under the first E, the X in Jolly Roger is under the second letter, the O. The third is under the E in Treasure Map, and finally the fourth is under the C in Blackbeard. 

And you take those 4 letters and put them into the text box, giving you "EOEC" and you win the game.