This is the Subwing, invented by Simon Sivertsen in 2010 the subwing works in a similar way to a fish fin, pressing the leading edge of the device down will cause the rider to dive, pulling up will make the rider surface and twisting it left or right will change direction – at least as much as the 15 feet of rope that you are being towed behind the boat will allow.
The wing is available in three versions, the fibreglass and epoxy version which retails for around $700 while the Carbon Matt and Carbon Glossy, both made from a 6k Twill Carbon Fibre retails for $850 and $895 respectively.