I hooked up my multi-meter to measure the current draw of my ROV and here are my initial findings.
Test #1 - Powered on sitting idle
Light percentage, Power draw
Test #2 - In the water
For this test I simply engaged the port and starboard motors in the forward motion. My multi-meter only goes up to 10A and it was very easy to draw that much current.
I found that at around 25% of full power the ROV was drawing about 9.8A, I left the motors running for 10 seconds and that is where it settled.
Although I didn't get a lot of data points about the current draw for the motors under various load conditions I got the general answer I was looking for....A LOT! I'm going to guestimate that the thrusters could easily draw over 20A to 30A depending on how much power you send to them. The ESCs can easily handle that, their specs say 18A continuous and 50A burst.
I'm able to have it in the water and use a multi-meter through the use of my external battery adapter thing, http://www.thingiverse.com/thing:94381