There were a few tasks to perform - we had to check our depth guages - mine reads slightly shallower than it should. We had to time each other doing a concentration task to test the effects of nitrogen narcosis. I completely stuffed up mine, I'm, afraid to say. A combination of not quiet understanding what was required, and watching other people at the same time.
As an option, we could also try eating a mini mars bar at depth. The mars bar must have a fair amount of air because the squish in quite a bit. With a great deal of coughing and spluttering I managed to eat it, and was quite pleased really. I think the fish ate more of it than I did - but thats OK, it tasted HORRIBLE mixed with salt water.