The balance between benefit and risk is central to the work of all those involved in aquatic services. The Hippocratic exhortation of Primum non nocere, “First, do no harm,” has a history of over 2000 years. Superficially, all would support this dictum, but harm can result from inaction. The balance between no or little intervention on the one hand and proactive intervention with iatrogenic risk on the other is complex and enduring. Risk implies that one does not have all the information available to know the exact likelihood of an outcome, a common situation involving rescue, first aid, and resuscitation. The theme of Primum non nocere (and its congener, risk-benefit ratios) in the aquatic rescue and resuscitation domain has both ethical (e.g., Good Samaritan) and legal (e.g., tort action) implications. Recently, a reversal in intervention philosophy, “Any attempt at resuscitation is better than no attempt,” has emerged. This aphorism is in stark contrast to the traditionally conservative, “Don’t do anything for which you are untrained.” Current and continuing research audits are needed to assess whether this newer paradigm results in a risk-benefit ratio low enough to counter the traditional Primum non nocere.