If you are in the mood for a nice day on an idyllic beach doing some snorkeling, you should definitely go to Blue Lagoon Beach. It is located about 1 hour drive (40km) from Ubud and Sanur.
There you will find fine white sand, palm trees, crystal clear water to observe a variety of fishes and gentle waves.
It is a nice spot to go with either with family or friends. You will find two warungs where you can buy snacks, refreshments or enjoy a local meal and you can even rent snorkeling gears and life jackets !
The access is really easy, you just have to pay a small parking fee and go relax on the beach listening to the sound of the waves !