Beaches of bali

In my first 312 hours in Bali I have noticed that all of the beaches are on the same bay.
The island is a HUGE volcano. When the volcano came out of the ocean and erupted, rocks came out of the volcano - big and small - over the years the small ones turned into sand while the bigger ones didn't. Most of the small rocks spat at the southern part of the island. Depending on where you are on the bay it has different names... For example if you are in Seminyak the bay is called "legian" and if you're in changgu then its called "Batu bolong beach"
And that's what i've learned in my first 312 hours in Bali.