Game Play
When you play "Deep Voyage" you click groups of three or more gems to make them vanish. The gems above them will then fall down to fill in the gaps that you created. You must have at least three of the same gem, though if there are more gems touching each other then those gems are also added into the group that will vanish when it is clicked. Simple enough, one might think.
Bigger Groups
While groups of three gems will be enough, it's always best to go for the bigger groups of gems first. The bigger the cluster of gems you can destroy at once, the more points you'll get and the faster you'll progress through the game. It isn't always obvious where the big groups are, so take a deep breath and look at the entire board before you just click the first group that you see that will disappear. If you rest your mouse on a group, then all the gems in that group will start to spin, showing you the size of it.
Three Moves Ahead
A good course of action is to try and look not just at your move, but at the consequences of your move. If you click a small group of gems, it could cause a bigger group above to meet up with another group of the same gems below, thus forming a larger overall group for more points. Causing chain reactions like this is one of the best strategies for clearing the board quickly.
Mines
"Deep Voyage" contains mines that, when you click on them, destroys adjacent gems. This can be a very valuable tool, especially if you position the mines just right, surrounded by larger groups. This gives you the ability to destroy huge portions of the field by using proper strategy. However, mines can also be used to clear troublesome areas to create further chain reactions.