Radioactive water is water that contains radioactive isotopes.

These isotopes are atoms that have an unstable nucleus,  

which means that they are constantly decaying and emitting radiation.  

The radiation can be harmful to humans and other living things, 

so it is important to be careful when handling radioactive water. 

There are two main types of radioactive water: Naturally occurring and man-made. 

Naturally occurring radioactive water is found in groundwater, surface water, and even in the air.  

It is formed when radioactive elements, such as uranium and thorium,  

break down and release their radioactive isotopes into the water.