Life as a seashell wouldn't be all that different from life as a human.
All throughout our lives we'd have various creatures find a place to dwell within us.
That's not too different from all of the friends and lovers that come and go from our hearts.
We'd get moved around and flipped upside down, used in different manners based on the needs of the current occupant.
How is that any different from the way we grow and move and change based on the people we associate with?

But it seems to me a sea shell has a happier ending than a human.
Humans die and are buried and life goes on without them.
But without the shell some creature will be unsafe, lack protection and comfort.
In the end some human will probably pick up that seashell and take it home, keep it safe.
That person will protect it, will treasure it, and might even display its beauty in his/her home.
After all of the years of hardwork protecting others, the sea shell finally gets to be the one taken care of.

I think I should like to be a seashell.
I can only hope one day a kind and beautiful person would dust the sand away from me,
take me home, and treasure me always.