Locale: Telegrafbukta Beach
Go to the Telegrafbukta Beach and use the Submarine.
After a 16 min. exploration, you'll arrive at The Helm of the Nautilus
items > Use the Ship's Helm Desert Island (Secrets of Sunken Monolith is needed here)
You'll arrive at Desert Island.
Items > Use the Door and you'll arrive at Castaway Beach.
Explore SW - S - W - N - N - NW - N - NE, and you'll be at Abonded Shelter
Items > Use the Desk to get the "Message in a bottle" (This step is optional. Not necessary)
Explore SW - NW - N - NW - N - NE - NE - N - N - NE - NE - S and you'll be at Abandoned Raft
Items > Use the Raft to get the "Speargun"
Explore N - SW - SW - S - S - SW - E - NE - NE - E - NE - SE, and you'll be at Dakkar's End
Items > Use the Tombstone to get the "Dakkar's Wedding Ring" (Shovel is needed here)
Explore NW - NW - E - NE - NE - SE - E and you'll be at To the Black Lagoon
Items > Use the Pathway Black Lagoon
Explore N - NW - NW - N - N - N - W - S and you'll be at Dead Scuba Diver
Items > Use the Corpse to get the "Dive Light"
Explore N - E - S - S - S - SE - SE - S
Items > Use the Pathway To the Black Lagoon and you'll arrive at the Black Lagoon
Explore W - NW - SW - SW - W - SE - SW - SE - SW - W - SE - SE - SW - NW - W - W and you'll be at Castaway Beach
Items > Use the Submarine and you'll arrive at The Nautilus - Desert Island
Items > Use the Airlock
Explore N - E - N - E - N - E - N - E - N - E - N - E - N - E - N - E - N and you'll be at The Shipwreck
Items > Use the Staircase Lower deck
Explore E - E
Items > Use the Door Captain's Quarters and you'll arrive at the Captain's Quarters
Items > Use the Box to get the "Dakkar's Pendulum"
Items > Use the Bed to get the "Trident" and the "Unholy Diver achievement.
Secrets of the Sunken Monolith
Items for your health
Please note, that if you do the following quest, as listed, you'll get 12 xp:
Secrets of the deep
Guide / Map