Answer:
There are approximately 1.3 billion cubic kilometers of water in the oceans. 1 cubic kilometer of water contains 1 trillion liters of water. Therefore there are approximately 1,300,000,000,000,000,000,000 liters of water in the oceans, which is 1.3 sextillion liters.
To get to gallons, there are 3.78541178 liters in 1 gallon. Doing the math, that means there are 343,423,668,428,484,681,262 gallons of water in the oceans.
That's 343 quintillion gallons, or put another way, 343 billion BILLION gallons.
That's a lot of water.
this is based on the volume of the sea.. so this isn't taking into account that there is a lot of life in there, fishes,plankton,bacterias,plants etc..
I don't know what the volume of all sealife put together is, but for instance;
There is a hermaphroditic zooplankton species in the Black Sea (average weight of each around 10 g) a total of 1 billion = 109000 Kg in the Black Sea at the end of the 1980s god knows how many there are now, and this is just one specific little plankton thingy in a small sea..
so over the entire oceans there must be one hell of a total weight..
oh and fiy; a fish produces 1.5 times it's own volume to urine each day :P
so god knows how much pee is created each day down there :D