If you search the Gallery area of this website for Crash Tender, there is a video showing my boat in action so you can see the speed.
The ESC is a Turnigy Marine50. Water cooled 50A rating. The motor draws a little under 20A but it is a good idea to have some headroom in case of problems. I have a 30A fuse in the circuit. The motor gets slightly warm in use, but the ESC stays cold.
Happy to try and answer any questions you may have.