We caught the shuttle and headed to the trailhead for the narrows.  Things to know:

• You need proper equipment.
  • The rocks are slippery and being in ankle to waist deep water for hours will takes its tole.  You don't want to be the person who shows up in sandals and rolls their ankle 15 times in the first 1/4 mile.  We rented neoprene socks, canyoneering shoes and walking sticks for about $25.
• Even in July when the temps were in the 90s+ it got a bit cool in the more narrow parts.  I brought a windbreaker and was glad I did.
• Waterproof your phone/camera.  I used a DiCAPac WP610 to keep my Sony Nex dry and a DandyCase to protect my iPhone (also note that all of the pictures on this page were taken through these cases):