That boat still had probably 30-40 gallons worth of air in it when it was underwater with no paddler in it if the boat was vertical (which it looked like). It's a simple sum of forces, and that's a good amount of buoyancy force pushing the boat up.
Sum of forces on boat
Speed at surface of water = a*time under water
Solve those correctly, and I bet you come pretty close to how high that boat went.
Although it's going to be a transient equation since the bouyant force pushing the boat towards the surface is going to change as the boat rises to the surface
And as a positive thing to make this all happen, if the boat was completely vertical when he got sucked out, the nose (pointing down) would fill with water, while the tail would still have air in it since there's nowhere for the air to go. With the nose down and full of water and the tail up and full of air, the boat would stay completely vertical while it rockets to the surface since the tail would be the only portion pulling the boat to the surface. Pretty cool actually.