This is one of the better ones I've seen. It looks actually pretty 3D.

Make the image as large as you can on your screen while still having it all visible. I don't recommend a phone - try it on a monitor. Don't try to see the whole image at once - look at one small part. Play with the focus of your eyes until you start to see an edge forming - and when you do, lock onto the edge until you can see it without struggling. Just try to make the edge clearer without bothering with the larger shape yet. Once you do, it should be easier to hold the focus as you look around the image and actually pick out what shapes everything is making.

I recommend focusing on this part of the image as you start - there's a pretty cool sea turtle there. Don't use this version with the red scribble, the red scribble makes it noticeably more difficult.