For ocean/water vaporization feat, I prefer to use Q = MC(Delta T), thus...
M = mass of ocean =
1.37e21 kg
Assuming average temp of ocean is 10 degrees, and 100 degrees is boiling point.
Energy required to heat water up to 100 degrees:
Q1 = (1.37e21kg)(4186J/kg*c)(100 - 10 degrees) = 5.161e26 Joules
Latent Heat Vaporization:
Q2 = (1.37e21kg)(2705000J/kg) = 3.706e27 Joules
Q1 + Q2 = 4.222e27 Joules, or ~
1.01e18 Tons of TNT. Barely into the exatons range.