Even better, you can build an osmosis power station and create a lot of electricity. The energy in the salinity difference between the water of a river and the water of the ocean is enormous.

(It basically works like this: You have two containers with water of different salinities, connected with a membrane that only lets the water pass, but not the salt. The water will move through the membrane to balance the salinity - osmosis - and one container will have a rising water level, which can be used to generate electricity with turbines.)