Snorkelling is the casual act of putting on a mask and snorkel and looking below while floating. Snorkellers may not have any training and generally spend most of the time on the surface. Skin diving takes snorkelling a step further by adding short dives underwater. Skin divers may have training that teaches skills, such as efficient dives and snorkel-clearing. Freediving uses advanced breathing techniques and diving skills to increase depth and time underwater. Through training, freedivers learn conserve oxygen while breathholding while practising different freediving disciplines, such as static apnea, dynamic apnea, free immersion and constant weight freedives. PADI Freediver course – Develops the knowledge and skills for basic static apnea, dynamic apnea, free immersion and constant weight freediving from 10-16 metres/30-55 feet. When completing open water training is not feasible or desirable, students complete just the knowledge and confined water skill portion of the PADI Freediver course (6 metres/20 feet maximum) to earn the PADI Basic Freediver rating.