I am supposed to be "Almost Inactive". But it just hit me and I had to get it out of my system.

What I am about to calculate here  is not a specific feat for a specific character. It's for causing a flood that can drown the entire planet. This feat is seen in many fiction. So I felt like there should be a calculation for this.

Now, when someone says "drown the entire planet" I take it as drowning the land since I don't know how one drowns the ocean.

The area of earth's land is 1.4894 * 10^14 m^2. Now to drown land one would have to drown what's on it. The tallest tree on earth is 115.61m. I will use 100m as the average height of water above ground. In the 21st century there are skyscrappers that are close to 1 km tall but I think 100m average height of water above ground is reasonable.

So, the amount of water needed is 1.4894* 10^14 * 100 = 1.4894 * 10^16 m^3 =  1.4894 * 10^19 kg = m

Now to drown the planet one would have to use the ocean water. The surface area of ocean is 3.61132 * 10^14 m^2 and the amount of water needed is 1.4894 * 10^16 m^3. So using all the water from the depth of 41.24m is enough.

In reality one wouldn't do it that way. One would use all the water from the nearby ocean not bring water from all over the world. But regrettably that's just unquantifiable.

The average height of land is 840m. So, the height we will have to use in our potential energy calc is (100+41.24)m/2 + 840m = 910.62m = h

$ E_p = mgh $ = 1.33 * 10^23 J = 31.77 teratons of TNT equivalent = Country level

Now raising the water isn't enough to drown the planet. One would also have to move the water from ocean to land (regrettably that is also unquantifiable unless we know every detail). Still, Country level is kinda disappointing.

This method was by directly using the water of ocean. One could also do it by causing rain.The amount of water in the atmosphere is nowhere close to the amount of water needed to drown the planet. So one would probably have to vaporize ocean water, send it to atmosphere and bring it back as rain. Meaning we have to calculate the value for vaporization of the said amount of water and multiply it by 2.

Average surface temperature of earth is 15 degree celsius.

So, $ E = 2[ ms \Delta \theta + ml_f] $ = 7.8 * 10^25 J = 18.654 petatons of TNT equivalent = Continent level

Now, in every case I saw this feat is rated as Multi-Continent level (for example on the pages of Zeus (Percy Jackson) and Death (Supernatural)). Well, in reality it would be Multi-Continent level if one day what I suggested here gets accepted. But until then this feat is not anything more than Continent level.