I just made a rough estimate from that footage based on looking at a point on the ocean where it breaks the water and then timing how long it takes half the length of the boat to pass that point, which is about all you can do since the wave and spray obscures stuff soon after. Not very scientific, but it works out to around 21.5 knots by my estimation. Of course that is if the footage is not slowed down at all, which to be honest, it looks like it is a little.

Chock