Check out the map and you’ll see that Tateyama isn’t only ALL BEACH but EVERY KIND OF BEACH — gentle and wild, sandy and rocky, bayfront and ocean, in little coves and wide-open to the sea.
For details, see:
https://tateyamacity.com/foreign/mountains-and-coastlines/beaches
and
https://tateyamacity.com/foreign/mountains-and-coastlines/okinoshima