How would being able to bring water into the gills when the mouth is closed benefit a bottom-dwelling shark or ray?

The ability to bring water into the gills when the mouth is closed would benefit a bottom dwelling shark or ray, because it would allow them to be more discreet when in the process of catching prey and they would be able to stop swimming. Most sharks have to continuously swim or else they would sink, while being able to bring water into the gills when the mouth is closed would highly benefit them and allow them to stop swimming for a moment.

Explanation:

I am not 100% sure this is the correct answer, but I am currently doing a lab on this, so I am using the knowledge I previously had and online resources. I am pretty confident though.