"What's the plural of beach?"

The plural of beach is beaches.

Definition of beach:

A landform along the shoreline of an ocean, sea, lake, or river, consisting of loose particles such as sand, pebbles, or gravel.

Single Examples:
1. We spent the day relaxing on the sandy beach under the warm sun.
2. He enjoyed swimming in the crystal-clear water of the beach.
3. She walked along the shore, collecting seashells on the picturesque beach.
Plural Examples:
1. They explored several beautiful beaches during their vacation.
2. We built sandcastles and played beach volleyball on the crowded beaches.
3. The region is known for its pristine beaches and turquoise waters.