Question
what kind and were can I buy the soil for water lilies. what do you call it? I have fish so I don't want soil seeping out into pond

Answer
You can buy branded soil from reputed supplier is one option
Second option any loamy soil will do for the water lillies
loamy means that soil does adhere to each other and does not spread when kept on the ground if made a ball
This is required since it would not spread in the pool