1: Right at the start of the level, after you get the record and play the music, hit the gold rocks to the left with a laser and grab the gold page sitting behind it.
2: Swim to the left and up after you flood the sub and the gold page will be near the ceiling.
3: Once you are outside the sub and following the passageways, there will be 5 chests that you need to shoot open to get the gold page. They are all easily spotted and all along the route you need to take. One will be just after the save terminal that appears, the next will be just down the passage a little bit, the next two will be along the passage to the right, and the final one will be at the bottom of the large cavern you enter with the swordfish swimming around.
4: As you make a right from where the gold rocks on the left were, you will see this gold page floating. Simply go up to the left side of the page and swim through the wall on the right to be able to reach it.
5: Once you reach the Dark Depths, swim all the way to the left side when you reach the school of fish that push you. Go all the way until you reach the pufferfish there and then swim down through the ground to find more pufferfish and the gold page to the right.