In Into the Blue, you take on the role of a team of divers who are seeking mysterious treasures hidden underwater, but you are not the only one who wants to grab these sunken wonders. Explore the depths and try to bring the most precious items to the surface. Mark your presence in the different areas to control them and claim their riches.

On a turn, you roll the six dice up to three times, keeping and re-rolling dice as you wish, to simulate a dive. Dice show the numbers 1-5 and a treasure chest, and when you stop rolling, you place shells on one of the levels that you reached. If, for example, you rolled 1-1-2-3-5-5, you place two shells on level 1, one shell on level 2, or one shell on level 3. You can't place shells on level 5 because you didn't dive through level 4 to get there. If you roll a perfect sequence of 1-2-3-4-5-chest, then you grab one of the five random treasure chests, which are worth 5-8 points, then take another turn. If you don't roll a 1, then you don't place any shells at all!

When the fifth chest has been claimed, the game ends immediately. Alternatively, when someone places their last shell, each other player takes one final turn. On each of the five levels, whoever has placed the most shells scores the main treasure token for that level; whoever has the secondmost shells takes the secondary treasure token, and in a game with 4-5 players, the player with the thirdmost shells also scores. Ties are broken in favor of whoever has the most shells on the level immediately above the one being evaluated. Players sum their points from tokens and chest, and whoever has the highest score wins.