Solo diving was considered technical diving by most recreational diver certification agencies and discouraged as more dangerous than buddy diving, but many experienced divers and some certification agencies consider it an acceptable practice for suitably trained, equipped, and competent recreational divers; some others consider it occasionally inevitable. In place of relying on the buddy diving safety system, solo divers try to be self-sufficient and are willing to take responsibility for their own safety while diving. The first training agency to offer a Solo Diving certification was SDI in 1999. In 2011, the Professional Association of Diving Instructors (PADI) started offering a solo specialty called "Self-Reliant Diver", which in many respects (entry requirements, for example) is very similar to the course offered by SDI.