Go to the very bottom and keep going right. Go in the door and up to the Buddha statue. After completing the level, you will get the Pneumatic Speargun as a second weapon alongside the mandatory one.
Dive down and look for something yellowish in a crevice. You will find a fat rich man's camera. Find the boat to get the High Tech Fins.
When you first start, go to the bottom and go left. When you reach the mountainside, follow it to your right all while staying at the bottom. If you do not do this, it will be easy for the sharks to attack you. Eventually you will see a crevice in the mountain to your left. Go in it and look down. You will see a gold necklace. Swim to it, then get back out and kill the two yellow sharks to get the Improved Suit.
Go to the back of the ship where the propellers are located. Go down the second or first step, turn around, and go through the door that appears. Go up the stairs and turn right. Go into one of the doors and you will see the Lost Diver. Kill the two Hammerheads to get the Improved Tank.
Go to where the Bull shark is located. After swimming away from the tube from which you entered his enclosure, head down and look near there to find a treasure chest. You will get the Improved Fins when you complete the level.
Go 5 degrees north and swim down the underwater crater. Turn around and swim through the ivy to find a little pop-bottle mini-sub.
When you first dive, go down to the bottom, take out your weapon, and just wait. Do not move because the Great White will come to you. He is not that difficult to deal with if you stay at the bottom because most of the time he cannot swim down that far, but will go over top of you. Just take your time. About three shots are required to kill him, depending on which gun you use. When heis belly up, go northwest with the little dot just barely above the west direction on your compass. When you can go no farther, turn southeast with the little dot on the red energy bar. Keep going this way and you will reach a crater. The mini-sub is in the crater. Note: There is also a Tiger Shark. It is best to take care of him before you go in the crater, as it is very dark in there.
To find the minisub, go to the crater and down to the very bottom. Get next to the wall and follow it until you see an opening in the wall. Go into the opening, and inside is the mini-sub.
Swim around until you reach the main box-like "temple". Enter it and follow the trail or the one in the hidden door near the temple's door to find some old worthless pottery called "Priceless Treasure". After killing the Lemon sharks, you will get the Heavy Pneumatic Speargun.
Successfully complete each level in career mode to unlock the "Mystery" level. This level requires that you find and kill a Megatooth shark.