At your first dive, you will receive an introduction to the Scuba Diving equipment and the basic knowledge that you need to enjoy the time underwater safely. Your adventure starts at a very shallow depth, where you have time to get used to the sensation of breathing underwater.
Your instructor shows you the basic skills and lets you train, so you can handle your gear, and will then take you on a nice tour. Still at really shallow water, you can enjoy a full dive without any complications.
After a surface break, with some cookies, water and the briefing for the next dive, you get back into the water with a fresh tank of air. Some more skills, and you will be prepared to dive to a maximum depth of 12m - you don't have to go that deep if you prefer to stay shallower.

After successfully finishing these two dives you will receive the SSI Basic Diver certification, which allows you to do more dives to a maximum of 12 metres in the next 6 months, and can count towards your Open Water Diver qualification.