It decreases?

If the air pressure increased, wouldn't that make the diver go down? What happens when you press on the pressure cap?

Oh, yeah. So, at night the atmospheric pressure increases and therefore the diver sinks?

Can someone help me with this question about a Cartesian Diver:

You painstakingly adjusted the water level of your diver so he is just floating and your treasure is just sinking. You come back the next morning and find your diver sitting next to the treasure on the bottom of the bottle. Knowing that your bottle was tightly capped, how can you explain this?

I think the answer has to do with the level of the water in the diver. It must have changed. I don't really know why though.

What happened to atmospheric pressure overnight?

Why is the atmospheric pressure higher at night?