Nothing will happen.
Consider a lightning rod. A lightning rod provides lightning with a conductive path from a spike atop the building or tree down to the earth. Rather than travel through the poorly conducting building and start a fire, electricity takes the easiest and most conductive path to the ground through the lightning rod and associated metal wire.
In your scenario, the salt water provides the most conductive path. Salt water is an excellent conductor of electricity. Things in the water will be less conductive than the salt water, and the electricity will go around them unless it hits something directly.
When lightning hits the sea, most of the electrical current spreads
radially outward on the surface. Because seawater is a good conductor,
the remaining current penetrates hemispherically downward and fully
dissipates less than 10 feet below the surface. It is believed that
lethal current spreads horizontally only 20 feet from the position of
If a tremendous amount of electricity is poured into this endeavor, it will heat up the salt water like any other conductor. Water has a high heat capacity and it requires a lot of energy to raise the temperature of water a degree - more than just about any other substance. Most of the electrical energy will not go to raise the water temperature, but will pass through the water on the way to the earth.
There is much water in the ocean. It will take godlike amounts of energy to raise the temperature of the ocean any measurable amount.