You may have done this already, but there are two silver hatches on the sub. Blow them up with explosives, and there will be some switches there. Jump on one, and then the other character should jump on the other.

This is another Treasure Chest, but I believe I already covered how to get this one before. Go ahead and look back on the other pre-Free Play section on Opening the Ark in order to see how to get that one.

The only other thing to do here is go to the other side of the sub, and go left. Use Indy and the whipping platform to get a ladder to the next level, then become a smaller character to go through the crawlspace. You will now have the Eighth Treasure Chest when the small character comes out the other side.

Go to the one area that requires you to rebuild a car. Move the car, and you will see some hieroglyphs. Translate them, and you will enter into a new area. You will see some yellow and gold tower looking things. Push the first one on the tiles to the right. Then destroy a box that is on the other set of tiles and rebuild them into a solid path. Push the yellow and brown tower to the left over there.

What you need to do now is jump on one, and wait. Your other character will jump on the other one automatically. I remember that I tried to do this by switching off, and never could get it to work. Apparently, the other guy kept wanting to move off. All you have to do is wait, and when both the tops of the golden towers are pressed down, the floor will open. You can jump down and build a ramp leading out of it. You will need that ramp when you grab the parcel and take it up to the mailbox in the corner.

When you leave this area, you need to go into the horse pen area and dig in the center. You will find the Ninth Treasure Chest there.

There is one more Treasure Chest to be found, and you will need to go to that one area where you had to make that weird number 4. When you reach the area where you need to face off with Belloq, go to the area with the hieroglyphs, and dial in the combination. The Tenth Treasure Chest will be right there.