The Sea Witch was an ancient Earth clipper ship built in 1846.
A model of the Sea Witch was in the possession of Henry Janeway, who displayed it next to the register of his bookshop in 1999. (VOY: "11:59")
The same model or a very similar one was later owned by Travis Mayweather, who kept it in his old quarters aboard the ECS Horizon. (ENT: "Horizon")
Its launch date and Clipper designation can be seen on its stand.