I have an excellent raft made by Sevylor. The Sevylor rafts really are very sturdy and they only cost around $100. I love fishing out of the raft (comfortable and easy to swing around to take an extra cast at breaking fish).
I actually used my raft as a mode of transportation when I was in Alaska a handful of years back. I logged 5-10 miles as I rowed my way across various lakes on Admiralty Island. I loved that trip. I enjoyed the best day of fishing in my entire life while on that trip - but that is another story.
One day the wind creamed me while in the raft. Adrian is correct.
In fact the Sevylor raft looks very similar to the raft in the link that you posted!
If you are looking to use it in the salt then you should realize that the short oars that fit through the oarlocks do not get you moving very quickly. I would not feel safe in moderate current. It is perfect for freshwater though. I enjoy fishing from the raft far more than I enjoy my float tube.