The Tonle Sap is a very large river, which at one point becomes as wide as a lake. Traveling along this river is an interesting way to reach Siam Reap from Pnomh Penh. While the slow boats take a couple of days to make the journey, it is easy to find fast boats which take only half a day. It is preferable to arm oneself with sunscreen and sit on the top of the boat (which will be overcrowded), to get a better view, more fresh air, and improve your chances of survival should the boat capsize.