Portable playhole February 11th, 2020 2002-05-01T15:30:52+12:00 A kayaker and engineer in the USA have built the Wavebox, a portable, artificial play hole. According to TechTV’s Portable Whitewater Practice Ground the pumps put out 6,400 gallons per minute – that’s about 0.4 cumecs. For a bit more than $120,000 NZD.