What is blue but does not weigh very much?

Light Blue

I was at the beach with my family, and we spent the day building sandcastles and collecting seashells. As we were walking along the shore, we came across a big sandcastle that had been washed away by the waves, leaving just a small mound of sand behind. My kids were disappointed, but I just chuckled and said

I guess that castle just couldn't weather the storm!

What do you call a belt made of watches?

A waist of time.

I'm trying to start a band, but it's a treble-making process.