Practice!! If you're still scared by next year, don't go through with it. People will be relying on you.
For now, practice going to the bottom. Do it in steps by going to the bottom at first in shallow water and then moving on gradually to the deepest water. At first in the deep water try diving and going straight to the bottom, and then you can work on surface dives. Surface dives take longer and require more power to get to the bottom than diving or jumping from the deck. You can throw a ring or some other object to retrieve the bottom for a target. If your facility has a 10-lb. brick, ask if you can borrow it to practice. It simulates rescuing a submerged victim. Also, practice swimming along the bottom of the pool. A lifeguard has to be totally comfortable in the water.
Best of luck!!
