Over a thousand years ago, fish and plants (that some are now extinct) lived a happy life.
After a while, they soon died out.They became more buoyant over time as bacterial decomposition produces gases inside the body.Then, layers of sediamentary rock build up on the bottom of the river bed.
After everything has been completed, coal, oil and natural gas can be found at the bottom of the ocean. The things that use fossil fuels are : Water, Alcochol, Gasoline, natural gas or anything that uses electricity. Coal also forms from deposited trees , which fall into the sea.Usually coal is made by plants and oil by animals.