Inside the fish monument now and I am in a room with 5 water spouts coming from the floor. It seems the 5 blocks need to be placed on top of the water jets but the snake moves way too fast that I am never able to get all of them down before he knocks them off.
There is a platform at the back wall of the room. If you stand on it, you will deactivate the snake. Throw all of the stones up onto this platform and then stand on it. When the snake deactivates, you can aim and throw all of the 5 rocks at the water jets to block them off and complete the puzzle