A slightly more time-consuming journey than some of its neighbours, but Hayama Isshiki beach, aka Isshiki Kaigan (一色海岸) is definitely worth the effort. A beautiful stretch of sand so nice that the Emperor himself has his summer home right on the beach.
In the summer there’s a tropical feeling: the police guards pacing the royal beach house walls are not there to stop you drinking beer - or even having barbeques - and seem pretty content to get in the beach vibe.
Perhaps we have the royal presence, or the extra travel time to thank, but it means getting a space on the sand is possible without too much hoo ha. It also means the sound of nature wins over against human chaos and music. If shade is more your scene, there’s a nice area sheltered by trees, and if sitting on (or pitching a tent on) green grass is your taste there’s even a nice little spot for that.
There’s some really good swimming to be had in the bay directly in front of the Emperor’s house. An artificial bay of flat, calm water, flanked by a large concrete kind of sea wall/pier, and no bad currents