Calc Ninja Slayer - Darkninja blows up boat

(http://imgur.com/uuiZ1CZ)
Darkninja blows up a boat. We're given a nice fireball, so this should be simple enough. The average height of a Japanese man is 170.7cm (1.707m).
43 pixels = 1.707m
1 pixel = 1.707m/43 = 0.0396976744m
0.0396976744m X 1018 = 40.4122325m
40.4122325m/2 = 20.2061163m

Using Nukemap for fireball radius, we get a yield of 16 tons of TNT. Alternately, using the MIT nuke calculator we get a yield of 141 tons of TNT for fireball radius at breakaway for contact surface burst.

Final Results
Darkninja blows up boat (low end) = 16 tons of TNT
Darkninja blows up boat (high end) = 141 tons of TNT