The submarine is unlocked by completing the elite fishing achievements.
The submarine takes 2 days to return from its trip.
The following items drop from the submarine: (Note the current amounts and drop rates are from a small dataset)
|Sea Molten Glass||2-19?||100%?|
|Raw Angler Fish||1-2?||33%?|
|Ancient Broken Key||1-2?||66%?|
|Mixed Treasure Chest||1-2||5%|