I like the beach a lot, but I've never been able to feel truly relaxed in one as there's always more people around and with more people more often than not comes shouting, laughing, loud music, etc. I think I associate the beach with being active and joyful, than being in zen-mode.
My idea of relaxation would be at my house, reading my books and magazines on my iPad or playing a solo TTRPG with an ice-cold carajillo or rompope cup in hand, with Portishead, Massive Attack or Nortec Collective playing in the background, during those late summer/early-mid fall months here in Mexico City in which you can hang in the garden, balcony or whatever, and the weather is just warm enough to make you feel cozy, while a breeze of fresh cold air hits you now and then, feeling the best of both worlds.