Siem Reap to Phnom Penh by river

There are boats, but the lake levels are very low at the moment. Actually all you will see for the most of the 6-hour journey is miles and miles brown water. By the way, few of the boats carry enough life jackets for the number of passengers aboard. Why don't you take flight. The flight fare is even cheaper than the boat fare and it only takes less than one hour.