Being a vampire pony in a seaside town is torture. Let's list a few reasons, shall we? Let's see...
Sunny 24/7 and always wearing a cloak.
Everyone thinks you're weird because you never go to the beach or anything.
That cloak is so stuffy!
"Omg, you need to get out guuuuurl! That cloak is a fashion criiiimmme!" Say the popular fillies.
Well, Serena Star had to deal with that, plus more. In fact, a group of colts suspected her to be a vampire (which she was), so they challenged her to stay on a beach for an hour. IN A FRICKING BIKINI. The beach thing was enough. They now want her to do it in a bikini? Why not just a normal swimsuit?