How long has the water on earth been around?

The water on the earth has been around for about 4.6 billion years

The study pushes back the clock on the origin of Earth's water by hundreds of millions of years, to around 4.6 billion years ago, when all the worlds of the inner solar system were still forming. Scientists had suspected that our planet formed dry, with high-energy impacts creating a molten surface on the infant Earth.

Answer: 4.6 billion years.