The course lasts 4 or 5 days and is divided into classes in a swimming pool or pool-like waters (2 days) and classes in open waters (2 or 3 days). During this time, there are also theoretical classes (lectures, film, and self-study from the textbook). During underwater classes, you will learn several skills you will use later almost automatically.
During the course, you will learn, among other things, how to prepare your diving equipment, perform checks on your partner before diving, enter deep water with all the equipment, replace your snorkel with a regulator and vice versa, find your regulator underwater, take off, put on and rinse your mask under water or use a backup air source. But most importantly, you will learn to control your buoyancy. Suspending in the water (so-called hovering) and regulating your position with just your breath will no longer be a magic trick and will become a regular skill.
The OWD training will also prepare you for the next, slightly more demanding course: Advanced OWD.