Jamais' entry on sea power reminded me of Yusuke Obuchi's Wave Garden, last seen at Cooper-Hewitt's National Design Triennial. Although we know nothing about potential negative ecological impacts, as a proposal for an artificial floating landscape and power plant, it's beautifully speculative:

"The Wave Garden consists of 1,734 three-inch-thick ceramic tiles linked together and supported on the water's surface by tubular buoys. During the week, the motion of the ocean's waves causes the flexible tiles to bend, generating energy through piezoelectricity (the electric charge produced by mechanical stress on crystals). Demand for the energy the Wave Garden produces on weekdays determines its function on the weekend, when energy consumption declines. If Californians have consumed little energy, they are rewarded: the tiles rise to the surface to form recreational platforms and swimming ponds. But if weekday demand is too high, the garden remains strictly a power plant. Acting as a barometer of energy use, the Wave Garden makes invisible power visible.