Sir,Recreational scuba diving may induce cardiac arrest due to drowning, decompression illness (DCI) or the occurrence of internal disease; however, there have been few reports that have analyzed the fatal compared with surviving cases in such circumstances. Accordingly, we retrospectively investigated the features and outcomes of patients who experienced DCI during the recreational diving.A medical chart review was retrospectively performed for all patients who had DCI after recreational scuba diving and were transported through the physician-staffed helicopter emergency medical services between March 2006 and June 2013. Subjects were divided into two groups based on whether they had experienced cardiac arrest (arrest group) or not (control group). The six cases were treated as the arrest group and 55 cases were treated as the control group. There were no significant differences concerning the sex (male/female: 3/3 vs. 35/20), age (45.5 ± 6.2 vs. 42.7 ± 1.7) and ratio of emergency surfacing (yes/no: 5/1 vs. 35/20) between the two groups. The ratio of the occurrence of cardiac arrest in the summer season tended to be lower than that during the non-summer season (20 vs. 129%, P = 0.06) and the ratio of amateurs in the arrest group tended to be higher than that in the Control group (100 vs. 68%, P = 0.05), however, these differences were not statistically significant. All the subjects in the Arrest group died and all subjects in the control group survived (P < 0.0001).A previous study reported that diving accidents, including cardiac arrest, tended to occur in the summer season, when the number of recreational divers is thought increase.[12] Although, Mekjavić and Kakitsuba reported that a cold environment promotes gas formation during hyperbaric situations due to the malperfusion of soft-tissue and[3] hence that risk of pure decompression sickness may be increases in non-summer seasons. The ratio of fatal cases per diving accident in the non-summer season was greater than that in the summer season (40 vs. 36%) based on the Japan Coast Guard announcement In addition, the total number of fatal cases during diving in the non-summer season was greater than that in the summer season on annual diving report 2008 by Divers Alert Network (39 vs. 36).[2] A previous study reported that dive injuries were associated with diver-specific factors, such as insufficient training and that the outcome of drowning was poor, similar to our present findings.[4] A diving instructors and medical staff are now having regular meetings to discuss ways to prevent recreational scuba diving accidents in Izu Peninsula. This activity might reduce number of drowning due to diving accidents. This study demonstrated that cardiac arrest after recreational scuba diving tended to occur in the non-summer season, among amateur divers and the outcome of such events was fatal.