Ocean surveys
While serving in the US Navy during the Second World War, Hess conducted Pacific echo-sounding surveys between operations. He brought ocean-basin geology and seafloor relief into the problem of continental movement.
References: [1]
Creation and recycling
A manuscript circulated in 1959 before his 1962 History of Ocean Basins. New seafloor moved away from ridges and old material eventually descended at trenches, allowing recycling without an expanding Earth. Robert Dietz also advanced the idea and coined the term seafloor spreading.
Testing the model
Magnetic-stripe interpretations, increasing rock ages away from ridges and earthquake zones beneath trenches provided supporting tests. Together these observations strengthened the picture of seafloor spreading and descent at trenches.