Well, to put it as simply as I can, it is Minecraft on water. That is only partially bound by the grid. In Raft, you are only bound by the grid with the actual buildings/raft. Oh, and any object that needs direct access to water to work. Like anchors, paint mill and similar. Furniture, plant beds and similar objects can be placed wherever you want them as long as they have a solid foundation underneath. You obviously can't place them on water.
I have found the game rather recently and I absolutely had to have it. So I bought it from steam and I'm loving it. Like Minecraft, it has several difficulty options. I started on easy and then found out that you can get everything even on peaceful so I created a new world on peaceful (you can't switch difficulty on an existing world) and never looked back. Peaceful is the only one where the shark (yes, there is this annoying shark) doesn't eat your raft. It will still retaliate when you attack it (as will anything else) but nothing will initiate the attack. Peaceful simply makes it so much easier to gather stuff from the sea bed around the islands you happen upon.
