10 Days Under the Sea is a hidden object game with a treasure hunt theme, where valuables have to be collected around the world. The main character is an underwater explorer, and each screen is a submersed location with fish swimming around. Like in all games of the genre, each screen/location is filled with objects that must be retrieved within a time limit.
The player can take photos of the passing fish. These pictures are added automatically to an album with information about the species. Fishes with an ? sign give extra hints when photographed. There's a horn to scare the fish and clear the screen, and a food dispenser to attract them.
Four artifacts, stored at the bottom-right corner after being found, help the search for hidden objects. The lamp glows more brightly when the cursor is near a required item. The bomb captures all surrounding objects where it lands. The sensor beeps when it is close to one of the items. Poseidon's net automatically captures an object when clicked.
Standard mini-games (jigsaw puzzles, concentration) are included as well. After solving them, the player receives a piece of the magic compass and the game moves to another part of the globe.