Seminyak continues the long sweep of beach past Kuta and Legian. A sunset lounger and an ice-cold Bintang on the beach at sunset is simply magical. A good stretch can be found near Pura Petitenget, and it tends to be less crowded than further south in Kuta.
Less crowds also means that the beach is less patrolled and the water conditions less monitored. The odds of encountering dangerous rip currents and other hazards are ever-present, especially as you head north.