It is very obvious that everybody says water is very dangerous with electricity, but it is very important to understand why is it dangerous.
First it has to be said that water is a very good conductor of electricity. What this means is that if electricity travels and reaches water it will continue traveling when if it was for example wood it would stop travelling and moving.  Another thing that needs to be mentioned is that a human is also very good conductor of electricity.
You can become electricity’s path to the ground if you are touching water that touches electricity. Electricity would travel through the water and through you to the ground.

As a reminder, it’s important to keep all electrical appliances away from water and to make sure your hands are dry, and you are not standing in water when you touch anything electrical. 
We hope this helps you to stay safe.