okay im in the ship thre is a largee room with water ,but a little bit of air at the top,i found the hammer,where do i go now,this is confusing.

Do you have a key?

no,where can i find this key,and what is it needed for?

The key is very far down in the ship. The strategy I used was to swim through it first, killing all the man-eating fish. Then I went back for air, then went back through it to get the key. If I remember correctly it's all the way down to the bow of the ship. You'll quickly run out of air and need to constantly re-heal yourself once your air runs out as you make your way back to where you first came in, so you can take a breath of air.
I've heard you can first use the hammer to open the hatch which will provide some air for you as you try to get the key. It's a tough puzzle but you'll make it.

-Damian

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Fear is the path to the darkside.

Definately use the hammer on the hatch. Trying to swim all the way back would take just about every bit of your health packs.

Jamison

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"Ahhhh, medicinal herbs."