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Johannesburg-based inventor Mike Puzey's new 'Pumpabike' is a human-powered hydrofoil capable of hitting speeds of up to 30kph. There's only one problem: if you stop pumping up and down, the entire contraption sinks into the water. Oh, there's another problem: you can't just get back on and start pumping. Instead, you must launch from a boat or jetty to get the necessary initial speed to stay afloat. If you're willing to deal with those limitations, the Pumpabikes can be had for between $800 and $1,200, depending on configuration. (Thanks, Rick!)

UPDATE - Apparently this is a knock-off of the Trampfoil. Thanks, Kevin

Human-powered hydrofoil seeks jumpy riders [NewScientist]