Bottle Message

The Bottle messages is both a collection of miscellaneous quests and a series of paper notes in Fallout 4. Collecting each one gives the Sole Survivor quest marker to find a single levelled loot caches

Locations
Bottle message 2 is located behind The Castle, not far from the South-South-East most Star point. Near the water edge, not far from a largish rock standing by istelf near the water. Only the top of the bottle is visible. Taking the bottle creates a miscellaneous objective on the water surface, due East of Castle, and just North West of Spectacle Island. The thin antenna of a submerged boat is just above the surface. Diving down to the boat and taking the loot in the steamer trunk completes the objective.

Bottle Message 5 is located behind Mahkra Fishpacking, South East corner, near the rowboat with the Plastic pumpkin on it. When picked up, it marks a location on the surface of the water near a Buoy East of the packing plant with a miscellaneous objective. Diving deep below that marker is a coffin and a steamer trunk with assorted loot. Taking this loot completes the objective.

Bottle message 6 is located by the Nahant Oceanological Society, on the tiny sand island just off the coast to its south east.