Can i brine chicken in seawater? I have been smoking meat recently, and I found out that in Maine people brine lobster in seawater. Can I do the same in Florida with a chicken?
Some considerations: 

Typical chicken brines range from 5 - 10% salinity.

The sea averages 3.5% salinity (there are variables such as region, distance from estuaries, and weather that also impact ocean salinity).  Further, sea water is not just salt and water, but has other dissolved minerals, not to mention potential pollutants.  

Can you do it?  Sure, but what's your goal, and is the the way to achieve that goal?