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You do need to start early. You have to give yourself at least 4 hours each to get through the canyons. That is 8 hours total of just canyoning time. If you group moves slower than you need to keep that in mind.
Both canyons are technical canyons that require rappelling and wetsuits. Sundance Canyon finishes a dramatic 180 ft rappel that will get your heart pumping. Bear Canyon starts slow, though it finishes with a great narrows section that is tons of fun. Bear Canyon is a little deeper and colder than Sundance Canyon so your hands will feel great.
If you want a full day of canyoneering I highly recommend Sundance and Bear Canyon.