Apparently, there are still some out there to be found if you keep looking! This one seems to be in Holland.

And some enterprising GPS speedies have taken it a step further and dug their own canal, again in Holland!

www.surfertoday.com/windsurfing/new-speed-sailing-channel-unveiled-in-the-netherlands

Apparantly the canal will be unveiled at the first day of the 2015 Funsport Makkum GPS Speed Challenge on the 1st of April

maybe if they reduce the height of the windward bank they'll get the potential out of it

There is a difference between two Pictures. One is behind a sandwall and there wrote Carsten Hanke that he surfed on
this canal, He made 30 knots and a little.I phoned a friend in Makkum,he knowed nothing.He have a Surf school. So I looked in GPS and found Carsten Hanke. 30 Knots in Makkum. But not on a canal, it is open water. It is the pic. from his run. The other video with much green is not a new canal, I think a good joke for the first April. Carsten surfed on Saturday 21 March.
Wiolfgang