Elements from the earth's interior reaches the sea water through:
Under water volcanoes and volcanic activities
The mains conduit of elements from the earth's interior into the sea water is through under water volcanoes. The ocean floor has series of volcanic activities which brings materials from deep within the earth to the ocean floor.
These materials interacts with the ocean water and some of the chemicals in them are dissolved in it.
Some ashes and other debris from surface volcanoes can also fall into the ocean and be dissolved in them.
