Spongebob is trapped in the Flying Dutchman, but the boat is rising to the surface and Bob must go down before the atmosphere reaches him! You have to go down as fast as you can, passing by the interstices of the boat, so you need to be slippery, and for this you need to pass over the sea snails. You can also hide from your enemies in the Halloween pumpkins. There's many bonuses you can collect on the way (they'll give you points and extra lifes), but hurry up, because the boat is reaching the surface!
Arrow keys left/right to move on the ground, arrow key down to get you down through the cracks (you have to press it many times to go down). If you press alternately the arrow keys left/right you'll oscillate, what allows you to escape when you get stuck. Space bar to use the items.