The sea captain's hat is a peaked cover of a U.S. Navy officer of Ensign (O-1) to Lieutenant-Commander (O-4) rating. The cover features a white upper, black visor, a black band, gold chin strap, and the US Navy shield cap device.
- Southwest of Cambridge Police Station, In a boat sunken in the river. The area is littered with radioactive barrels and mirelurk hatchlings.
- Coast Guard Pier, can be found atop the roof.
- Faneuil Hall, can be found the display case near the door on the second floor in the room with lots of paintings and display cases.
- Harbormaster Hotel, found on the 1st floor: Room 61.
- Longneck Lukowski's Cannery, found in an open display case in the lobby.
- Western Bell vessel, in a sunken ship, follow the Nautical radio signal which can be activated at radio tower 3SM-U81.
- Sandy Coves Convalescent Home, found in one of the rooms.
- Warwick homestead, in the northern end between the concrete reservoirs in a funny arrangement on the head of a teddy bear riding a Giddyup Buttercup.
- South of University Point, directly south of the Sedgwick Hall building and directly east to where Billy Peabody is first encountered is a skeleton wearing the hat sitting in a bathtub near the water. Approaching the ship will spawn two mirelurk hunters (one of which may be legendary).
- Southwest of the USS Constitution; along the road, there is a large anchor on display next to a large stone sign. The hat is casually laying on top of said sign.
- Vault 88, going up a dead-end staircase and looking right. There's a statue wearing it and holding a X-cell.