How to retrieve two sets of relations in a bounding area

Hi. I want to retrieve all lakes and river relations in the UK.
type=waterway seems to cover rivers.
natural=water seems to cover lakes.
So I constructed the below but it only returns one of the two sets. How do I retrieve both sets of relations?
Feel I am not using sets correctly. And this type of query, where I want to get two different sets returned based on an area is something I want to do in general as well as for this specific river and lake query.
Many thanks for any guidance.

Not an answer to your question, but keep in mind that waterway=riverbank has been replaced by natural=water + water=river