In his 1551 Travagliata invenzione, the Italian mathematician Niccolò Tartaglia described a device for raising sunken ships. Despite his claim of originality, his contemporary Girolamo Cardano had described a similar method in his famous work De subtilitate, which was published a year before. A comparison between these methods reveals the uniqueness of Tartaglia's approach, for he combines an explicit defence of the horror vacui principle with an implicit negation of rarefaction. In this article I show the complexities of this conception (...) and stress the importance of keeping the personal argument between both authors in mind when interpreting their descriptions of wreck-salvage operations. (shrink)