We decided to take a long boat from the central pier and travel down the canals to Wat Arun. It was just 2 of us and we "splurged" on a private boat. It was interesting to see where people lived on the canals - some nice places and mostly not so nice places. At one point there was an older lady in a small boat selling trinkets and drinks and she encouraged us to "buy a beer for the boat driver", which we did!
We arrived at the spectacular Wat Arun and climbed the steep steps as high as we were allowed to for the beautiful view. I bet it would have been lovely at night-maybe next trip? If you have short shorts, you can rent a sarong to wear, right beyond the gate. My daughter did this and I think she received a deposit back when she returned the sarong. We stayed for about 45 minutes-it was very hot and quite a climb, so bring water and stay hydrated. Don't forget your cameras.
When we were ready to leave, we spotted our boat driver and waved him over to pick us up. It was a short, direct ride back to the pier. I think the entire trip was 2 and 1/2 hours, including the time at the temple.