Many different side quests in offer great rewards, but not many give you access to nuclear firepower like those in the optional mission. Irradiated beasts and mutated monsters are common sights as you explore the post-war Wasteland. However, you may be surprised by what you find trying to pursue a sighting of a sea monster just off the coast of the Boston Harbor.
Those looking to roleplay in as an ambitious cryptid hunter will be slightly disappointed to learn that this quest mostly involves talking to NPC characters. Try to have a character build specializing in passing speech checks to receive the maximum number of rewards possible from this mission. While you still need to fight several enemies, the best items you can obtain are done through conversations with NPCs.
Fallout 4's latest next-gen update may have broken the game but the addition of the Enclave proved so popular that one fan made it even better.
You can start the side quest by speaking to the NPC Donny Kowalski on the docks behind the Shamrock Taphouse. This character swears that they can see the of a dangerous sea monster out in the Boston Harbor behind the Taphouse building. They will ask you to personally investigate the issue and see if you can kill the beast before it threatens anyone.
Offering help will start the quest, but it becomes clear quickly that Donny has not seen any sort of monster and instead has mistaken a submarine's periscope for the appendage of some mutated creature. Unlike other quests that feature some sort of random encounter in when a mission starts, you have to actively pursue a new point of interest added to your map to continue.
Go toward the spot on your map labeled to discover a submarine hidden under the water. You can swim to this vessel to enter it and meet a Ghoul character named Captain Zao, who will give you the next steps to this quest. This NPC has lived for nearly 200 years and acts as the primary quest giver besides Donny, making him the one that gives you
Read more on screenrant.com