I got curious about drowning as a global cause of death tonight, so I did some research and found a paper by Etienne Krug et al. (2000).
The traditional view of injuries as "accidents," or random events, has resulted in the historical neglect of this area of public health. However, the most recent estimates show that injuries are among the leading causes of death and disability in the world. They affect all populations, regardless of age, sex, income, or geographic region. In 1998, about 5.8 million people (97.9 per 100 000 population) died of injuries worldwide, and injuries caused 16% of the global burden of disease (Krug et al. 2000:523).
The statistics on low- and middle-income countries are the most relevant. Drowning caused 22.4 deaths per 100 000 among children 0-4 years, making it the eleventh leading cause of death in that age group. The top ten were mostly infectious diseases (pneumonia, diarrheal disease, measles and malaria being the biggest), except for perinatal conditions and malnutrition.
The real importance of drowning was in the 5-14 year age class, where it was the fourth leading cause of death, accounting for 14.5 deaths per 100 000. That puts it ahead of diarrhal diseases for that age class, and more important than HIV, war, tuberculosis, and violence combined.
Drowning remains important for adults 15-44, as the ninth leading cause of death accounting for 5.7 per 100 000. It is a larger cause of death than maternal hemorrhage (although that applies only to women, naturally). In contrast, it was not in the top fifteen for older adults.
It is sort of unusual as a cause of death that has substantial importance for some of the lowest-mortality age classes. And it strikes me that it would be a substantial risk for a "coastal" adaptation -- exposing children to the water today (remembering that many aren't anywhere near water!) creates a global risk comparable to malaria.
Krug EG, Sharma GK, Lozano R. 2000. The global burden of injuries. Am J Public Health 90:523-526. PubMed