Random: This one was the latest mode to be implemented. You get randomly thrown into islands of varying shapes, terrains, weather, animals (I like killing those evil crabs), starting equips, backstories (OOOooooh), etc. Supposedly some islands are pleasant, while others would make you want to rip your shirt off and flip desks.
First and foremost, I was a bit awestruck with the environment of this game. Since, there were no tutorials really and I had no idea what does what nor how to craft or use anything, I was literally clicking randomly, and experimenting for about an hour. I hovered my mouse on the things that were washed ashore and though it tells me what I was suppose to do with them and their uses, it did not clarify how to do so, so instead of getting too frustrated I did a bit of exploring first. Every new scenery struck me as wondrous. The lighting and coloring adds a really nice ambiance to the game.
Note: As you read through, you will read how to craft, build, and scavenge in the game. I also did not watch any instructional videos on the official website to see how the learning curve of the game is.
I was all oooooohh, aaaahhh and shi. If my blue guy had a face, it would probably be all O_O or in non-asian smiley, :O
A couple of other features I really enjoyed were the day/night cycle ( you even get to experience sunrise and sunset!) and weather (when it rains in this game, it literally pours). For me it adds more of a realistic quality to it, especially since the Under The Ocean has a great sense of physics and gravity. While I was playing during the storm, things were even flying over my head (I think they were coconuts).