From up on the cliff or over in the Bingin warungs, sets rolling through Impossibles have the appearance of being some of the best waves on Earth. This is usually a deception - 90% of the time Impossibles is a sectioning, frustrating, impossible wave. However, when everything comes together, Impossibles can be flawless, and lucky surfers will experience epic, 400-meter, ultra-fast perfection. Impossibles is a difficult wave to predict. There does not seem to be any set rule for which swell directions, tides, swell periods or swell sizes will work best. Due to length of the reef and its relatively consistent angle to the coast, there is a very small degree window for the swell to peel off perfectly rather than in big chunks of sections. There are two main takeoff points at Impossibles: the top section and the bottom section. Generally the top section works better when it is smaller, and the bottom section will transform with a huge swell and a low tide. All in all, Impossibles can be a good option for surfers who are not quite ready for the heaviness of Uluwatu or Padang Padang. However, on the big days, Impossibles picks up a lot of swell, and surfers should take care to known how to get in with or without a board before they enter the water.
Source: Impossibles Surf Guide