The Dejah Thoris was the Fourth Doctor's houseboat. He took Leela and K9 Mark I to Mars to sail on the canals.
It was constructed similar to the houseboats on the English canals[statement unclear], with the words "I.M. Foreman (London)" stencilled on the cabin.
The houseboat was destroyed by the Last Martian, but the Doctor rebuilt it. (PROSE: Crimson Dawn)