When I was doing the background research for nominating Alan McClure to the OEC Industry Pioneers, I ran across the forerunner of the Mohole Platform. It was called the Armstrong Seadrome and as best as I can tell was the first real semi-submersible concept. Armstrong had patents on it, and some of the language in the patents talks about wave theory as it was known in the 1920s. (I know that Bruce Collip actually came up with the first practical design for the offshore industry -- however if the Mohole hadn't of run out of funds, the Mohole semi design would have proved practical -- and it was developed using the Armstrong Seadrome as the basis for the design).
Armstrong had 4 or 5 related patents which are quite interesting -- he was just ahead of his time. For example, I think all of the early tension-leg platform patents include Armstrong's patents as cited references.