There's a number of beaches around Hoi An and neighboring islands. Fine white sand (somehow managing to be scalding hot in the sun anyway), emerald water with soft surf, palm trees, little beach huts, and very affordable cocktail service. Not unlike Bali except only a handful of people enjoy the beach.
Finding a bicycle big enough for me was a bit of a challenge but I found one. Didn't break any speed records on this thing though.