Over the last few weeks, a new devlog series was released on the The Sapling Youtube channel, showcasing the upcoming 'Sea & Sandbox' update. It will include, among many other things, a planet editor, a season editor, algae and underwater animals. The first video of the devlog series:
https://www.youtube.com/watch?v=s3iQw2WYvwE
The last and most popular video of the devlog series:
https://www.youtube.com/watch?v=psqkZBXaitk
This new 'Sea & Sandbox' will be available for everybody on September 13. If you don't mind glitches and crashes, you will also be able to play experimental builds from August 16 onwards by opting into the beta in your Steam settings. The end of every devlog video shows you how to do that.
Furthermore, a heads-up: most players indicate the current price of the game is a bit on the cheap side, so September 13 will also see a $2 price increase... so if you already know you want to buy the game, you might want to do it now.