Only 8% participants reported written checklist use, 71% reported using memorized checklists, and 21% did not use any checklist.
The proportion of divers who did not dive was 6.1% among the written checklist users compared to 2.3% among the memorized checklist users and 14.1% among the no checklist users.
8% of participants (n = 33) reported routinely using a self-checklist (written pre-dive checklist), 71% reported (n = 301) using memorized checklists, and 21% reported (n = 92) not using any kind of pre-dive checklist.
The rate of mishaps among memorized checklist users was similar to no checklist users.
When memorized checklist use (referent) was compared with no checklist use, the adjusted rate ratio of major mishaps, minor mishaps, all mishaps, and unsafe conditions suggested that there was no difference between the memorized checklist group and no checklist group (Table 4).
Our results also suggest that memorized checklists are not any better than not having a checklist.
Written checklists have been effectively used in other high risk areas like aviation and surgery to mitigate the risk of mishaps (Haynes et al., 2009; Helmreich, 2000), but the effectiveness of different forms of checklists (written or memorized) in diving is not known and the prevalence of checklist use among divers presumably low (Acott, 1995; Denoble et al., 2008; Ranapurwala et al., 2014).
The rate ratio for written checklist use as compared to using a memorized or no checklist was 0.47 (95%CI: 0.27, 0.83) for all mishaps (major and minor combined), and 0.31 (95% CI: 0.10, 0.93) for major mishaps.
Since most of the memorized diving checklists utilize mnemonics, it may be inferred that mnemonics do not provide focused instructions, and divers may only remember the mnemonic and the broad categories the mnemonics represent, but forget or overlook the specific actions to be taken.
The crude rate of unsafe conditions for the written checklist users was 6.8 per 100 dives compared to 12.8 and 15.2 per 100 dives among the memorized and no checklist group (Table 3), a crude rate difference of 6.0 and 8.4 unsafe conditions per 100 dives, respectively.
