Nam O beach borders on the Bay of Da Nang, about 17 kilometres northwest of Da Nang city, north of the Son Tra peninsula -- you can get a good view of it from Monkey Mountain.
At high tide it resembles most of the coastline that runs between Da Nang and Hoi An, but at low tide a large area of rock and white sandy shoreline is exposed, other than a few wooden stilted restaurants that serve among other seafood dishes goi ca (Vietnamese sushi), fresh, raw fish fillets marinated in a local sauce and dipped in a spicy powder. From April to August the sea is calm, clear and packed with marine life, so it makes for a great secluded snorkelling spot. From November to February wind swells make it an excellent surf beach.
Once you've had your fill the mountain road west leads to the Son Tra peninsula. For now there really isn't anywhere to stay near the beach -- you'd need to look towards the resorts along the not-so-lovely Red beach, which is due to be connected to Nam O later this year by a new 800-metre long road that links to the new Nam O bridge. If you are a fan of fish sauce, the surrounding fishing villages are famous for producing some of the best in the area; even if you are not, buy some and gift it to your guesthouse host, they will love you for it.