Thank you for playing my game! <3 To reach one of the endings, you need to make the opacity of an image go up to 100%, covering the whole screen with it: the opacity depends on the distance from something, and you should keep pushing forward even if you don't see anything (the world has no borders)! If you find the photo of Dita Parlo, try to complete it to reach another ending!
PS: interacting with the lifebelt is just a way to go back to the surface ;)