# Maybe not highly technical in the purest sense.

#### natto fire

##### Diamond Member
I have been thinking of this for sometime, and I know that it is something that should not even be considered for some time. However, I was hoping to get some numbers about it.

I have been wondering how many man made vessels it would take to displace a 'respectable' amount (1/4", or about 6.3mm) of the ocean's 361 km/2. The main variable that I do not know, is the draft of most of the heavy barges and super-tankers.

I know the formulas, and it seems like it would take an extremely high drafts (or LOTS of ships) to even begin to factor this in. Considering seawater is almost 1000 times as dense as air, and not to mention the moon throwing around massive amounts of the stuff.

#### CycloWizard

##### Lifer
It looks like supertankers displace between 100,000 and 400,000 displacement tons, which equates to about 330,600 cubic meters of seawater (for the 400,000 ton ship). The figure for the surface area of oceans is about 361 MILLION square kilometers (from Wiki). How much of a rise this would cause depends on the topology of coastal lands. But, one might estimate based on a vertical coastline and assuming infinite curvature of the earth (a poor assumption, but I'm too lazy to correct for radial effects right now). This gives a number for the increase in average ocean height of 9e-10 meters. Thus, height raised = 9e-10*number of 400,000 ton supertankers. This means it would take about 7 million such tankers to raise the ocean level 1/4 of an inch.