Microsoft has released a new Windows 10 theme in the Microsoft Store.
The description reads:
Take a deep dive into the deep waters and discover what lies beneath. Giant sea turtles, jellyfish, stingrays, and more are swimming by in this free, 16-image theme set from Windows 10 Themes.
After downloading activate the theme by going to Start> Settings> Personalization> Themes.
The theme can be found in the Microsoft Store here.