you need at least 600w to get foiling, we have a sup foil which pops up at 9kmph and with a 200 watt (12v) motor running 24v we could not get past 6 kmph even removing the foils . if the rider were a small child pumping the board, maybe , mean while its almost 50 amps @12v if propped up so batteries need to be sizable. i have seen a couple at around the 40Ah mark capacity wise . a gearbox seems to be needed to power a good sized prop . Note that RC air craft props work under water thanks to Reynolds numbers being kind you just need 15x less of a prop that you do in air because of the density being near 800x more in water. My aim is 1000w plus motor, geared down to swing a 2 blade 300mm diameter prop with variable pitch to perfect the top speed vs launch . it isnt easy though . 
the turnigy water cooled esc is my pick https://hobbyking.com/en_us/turnigy-marine-180a-bec-waterproof-speed-controller-with-water-cooling.html , Turnigy aquastar motor with the lowest possible kv and a reduction box . no idea how to easily pistol grip control the esc yet . im quickly seeing the reason the efoil is $12500 usd ! https://www.liftfoils.com/