The Riptide is a commissioned tug boat of the U.S. Navy. The ship appears to have been towing a barge full of military equipment to an undetermined location up the Charles River.
The vessel is accessible from a series of makeshift staircases from an overhead bridge. It is also possible to access the location by swimming up to the ship through the irradiated river. There are two beds in the cabin on the ship, one additional bed inside an opened shipping crate upon the barge, and a cooking station on the deck.
If the raiders at this location have not been dealt with before starting the quest Diamond City Blues, there is a chance that they pick a fight with the triggermen, Trish and Nelson Latimer, interrupting the quest.
The wreck of the USS Riptide appears only in Fallout 4.