The sea just washes them away.
That thing you did. Do it again.
The best revenge is to always survive yourself~ Henry Rollins
Its what you do while showing off your new bikini on the beach:)
It's a ploy to get you type A+ people to RELAX for a few hours. Can't even go to the beach and just be...have to be doing doing doing, so there's sandcastles. Just busy enough that your brain is satisfied that you're not being lazy, but not so busy you go home tired out.
So that they will show Columbus where to go.