Sinuses and flotation: does the aquatic ape theory hold water?

The idea that people went through an aquatic phase at some time in their evolutionary past is currently undergoing a popular resurgence (see Foley & Lahr). This idea has even started to gain some traction in more learned circles; the late paleoanthropologist Phillip Tobias wrote in support of aspects of it in an edited e-book and a conference on the topic held recently in London was endorsed by celebrities such as the television presenter Sir David Attenborough. Despite (or perhaps because of) the lack of interest within the academic community, advocates of the concept continue to fill the media (and blogosphere) with challenges to the "savannah hypothesis" of the origins of people and to bemoan the fact that their views are not taken seriously by mainstream academia.