1. Opening the game- Tap the Boom Beach icon on your mobile device to open the game.
2. Headquarters leveling- If your headquarters is not yet at level 9, do what is necessary to upgrade your HQ to level 9.
3. Radar Leveling- You will need your radar at level 5 to unlock dive locations.
4. Submarine construction- Once your HQ is at minimum level 9, you get access to the submarine. When you are able to do so, build your submarine.
5. Exploration- When your radar is sufficiently leveled to reveal dive locations and your submarine is built, send your submarine on dive missions. You have the opportunity to recover sunken treasures. Unlike other buildings and missions, you cannot speed up submarine missions in any way, so you'll need patience if the missions take a long time. Tip: When possible, upgrade your submarine so it can dive deeper. You can upgrade to level 2, but beyond that, you must upgrade your HQ. Max level for submarine is 10, and your HQ must be level 17 or higher.