Lead researcher Stephen Lippard has revealed that the "boats" have been created by attaching a modified version of potent cancer drug cisplatin and folic acid to carbon nanotubes.
Experiments with the boats have so far shown that they can kill cells with folic acid receptors more effectively than cells without them, he says.
Since the receptors are most numerous on cancer cells, Lippard hopes that the new approach can target tumours in the body and spare healthy cells.
Cancer drug paclitaxil has also been loaded onto longboats.
The researchers say that they were too big to squeeze through the pores in normal blood vessels, but small enough to get into the vessels that feed tumours.
The findings of the study have been published in the Journal of the American Chemical Society, and Cancer Research.