pre-dive equipment safety checks are an application where the use of a written checklist has been shown to reduce the incidence of mishaps which could potentially escalate to incidents with significant adverse consequences. The use of checklists for pre-dive checks is generally considered good practice by recreational diver training agencies, but is seldom applied in practice. Pre-dive procedures include planning and organisation of the dive and preparation of equipment, which generally includes function tests of safety critical equipment and assembly of the scuba set. Occasionally a buoyancy check may be made for unfamiliar equipment. An effective pre-dive checklist would reduce the probability of failing to kit up correctly and completely before entering the water. Divers are trained to apply mnemonics to conduct pre-dive checks in training, but there is little or no follow-up to encourage their use outside of the training environment. Each training agency has its own "buddy check" mnemonic recorded in its training manual, but there is very little common ground between them, and two divers trained by different agencies to equivalent certification, are unlikely to be familiar with each other's buddy check system, while in theory they have equivalent qualifications and are considered competent to dive together. Solo divers avoid this problem by taking sole responsibility for their pre-dive checks, at the expense of losing the hypothetical double check of the buddy. Most of the memorised checklists rely on mnemonics, which are all short and very unspecific, covering a wide range of checks, surveys and preparations, usually using a single word each to represent a series of checks on several important aspects of preparation. These checklists do not provide focused instructions, and important details of the actions to be taken may be forgotten or overlooked, or missed due to distractions. It is not known to what extent these mnemonic checklists are used in the field, and none of them have been evaluated for effectiveness. The use of a written checklist which provides sufficient detail to ensure that all necessary pre-dive checks are completed is experimentally associated with a significant reduction in unsafe conditions before a dive, and mishaps during a dive. In some cases the identification of unsafe conditions during the checks allows corrective measures to be taken, after which the dive may proceed, without associated mishap, and in some cases the dive is cancelled and the possibility of associated mishaps avoided. Reasons cited for failure to