Is it normal to fantasize about underwater fantasies?

I get these vivid pictures in my head, I'll just be laying there and I think what inspires this maybe is I recently painted my room to a light cerulean blue *like the waters in FiJi look* but yeah,but it will come to me, I'm in this sapphire blue with iridescent black scarves hanging from above giving it a spooky feel slightly...and then make my way around the corner to a really hot merman-primarily guy though, like he doesn't have the flipper thing, hes just chillin but underwater and not dying, is this a normal fantasy?