are a few countries where further support is obligatory, generally a requirement to dive with a buddy, but in most places a recreational diver is responsible for their own safety and is legally free to dive without any support personnel. Recreational service providers may impose their own terms and conditions on customers, but this is generally a contractual option. Balance between safety and efficiency As both time and physical and financial resources are limited, there is a trade-off between safety and efficiency. If taken to extremes, concerns with safety could prevent all diving. This trade-off is acknowledged in occupational health and safety legislation, where precautions are required to be reasonably practicable, with reference to cost, benefit, available technology and other factors. Diving beyond one's training and experience Recreational divers are often cautioned not to dive beyond the limits of their training and experience, as this increases the risk to the diver, and possibly also to other members of the dive team. Superficially this may seem logical, but it neglects to consider that formal training is focused on learning specific skills and assessment is against a minimum acceptable level of competence in those skills. These skills are intended to allow the diver to manage a more general range of conditions implied by the certification standard, and greater competence in the new skills is achieved by exercising those skills under a wider set of conditions than those encountered during training, which are of necessity, limited by circumstances. In reality, the range of diving that is considered within the limits of their training is generally defined in the training standard for each level of certification.The additional condition of being within the limits of their experience is not always specified in the same way. Some agencies will specify that the diver is certified to dive independently in conditions similar to those in which they were trained, but they do not specify how the similarity can be assessed. There is also the matter of how and where the skills were originally developed and honed to become the standard practice taught to the learner in formal training programmes. These skills did not exist before the equipment was developed which makes them useful, so the pioneers of each mode of diving had to develop them from what was preciously available, sometimes while using unfamiliar equipment, often by trial and error. Exploration of a place where no-one has