```Uranium is dissolved in seawater at very low concentrations, only about 3 parts per billion (3 micrograms/liter or 0.00000045 ounces per gallon). But there is a lot of ocean water – 300 million cubic miles or about 350 million trillion gallons (350 quintillion gallons, 1,324 quintillion liters). So there’s about 4 billion tons of uranium in the ocean at any one time.```
