Lake

If you don't even know where to get started in tracking down those last few puzzles in The Witness, the big lake between the Shady Trees forest, the Town, and the Quarry might help.

The lake is actually a map of the island, containing unique markers that act as a handy way to track your progress in-game.

Lake Object	Represents
Lanterns	Lasers
Fountains	Obelisks
Flowers	Audio logs(Yellow flowers for The Caves)
Clams	Bunkers
Triangular leaves	Discarded panels

The first thing to do when attempting to 100% The Witness is complete the 11 main areas that house a laser. If you aren't sure how many lasers you've activated, an easy way to tell is to go to the lake and check out if there are any unlit lanterns. An unlit lantern represents an un-activated laser.

When all 11 main areas are done, you'll want to make sure you have all the bunkers open and the video pattern input into the Theater under the Windmill. There are six videos, meaning six bunkers, meaning six clams in the lake. If the clam is open, you've already gained access to the bunker, but remember you need to also input the video pattern, which gets added to your puzzle count.

There are also 14 discarded triangle symbol panels around the island. Solving each gets added to your total puzzle count. If you're not sure how many you've solved, head to the lake and look out for the bright orange triangular leaves floating on the water. Solving these discarded panels dims that panel's corresponding leaf on the lake, making it harder to see and effectively checking it off your list. If you still see a few bright orange triangles on the lake, though, you still have some discarded panels to track down.