I have a few things bothering me about this. Firstly, what good would a parachute do in a boat explosion? You could argue ejector seats but they are clearly being blown outward by the blast. Also, although I believe the writers meant this to be a death scene if they wanted to bring either of them back it's pretty plausible. Gasoline explosions are big and showy. They put out a lot of heat, sure, but they don't have much concussive force. In the case of a powerful waterbender like Noatak he may actually have come away with those scars he claimed to have before but likely little else. Tarrlok might be screwed due to the fact he was pretty much right on top of the gas tank and had no bending.