Here, we have a foil board rider at Blue Hills Falls on Saturday, April 10. The current there is fast enough to support foiling, if you attach a rope to the bridge and hold on while the water speeds by you and your board rises on its foil.
However, the situation changes when you let the line out to maneuver in the surf when up on the foil.
You have to be able to handle the incoming tide when it suddenly and unexpectedly twists and turns. Not many can do it for long, including this foiler:
(Blue Hill, Maine)