the 3 in the front COULD be wearing those no ankle socks as the boots are high enough to cover those. the one in the middle back with white shoes is most likely no socks.
what is wrong with no socks in a shoe/boot while on a beach?
i dont personally like to do that but have a few times with worn shoes that i dont care about messing up just to get to the water when the sand is too hot vs using flip/flops sandals.