Yes. It means I'm very good at it. I think it's because bread and butter is simple to prepare, and so this, too, is also simple?

[Wait a second. Then why do humans also call it a 'piece of cake'? Cakes are a lot more complicated!]

It does tend to be quite convenient, yes.

[Would a single piece make it any easier? I don't see how it would. You still need to make the whole thing first, right?]

At any rate, perhaps we should get back to shore. There might be more bubbles coming.