A try dive takes 30 to 40 minutes.
An instructor will
give you a safety brief and provide an overview of the equipment, showing you how it works.
In the water they'll demonstrate what's required and reassure you before you have a go.
You'll soon have moved on from ducking under the water, taking your first few breaths to finishing with a controlled dive.
Afterwards your instructor will then talk through your dive and answer any questions you may have.