Various classifications are used by different organisations to describe shark incidents although the actual motive of many events is often unknown. We thus propose a simplified classification based on the most probable cause. With the exception of stalking and scavenging, we consider these incident types as attacks, which we define as a violent action against a person or object regardless of intent.
Hit & Run (HR): Improvised and spontaneous attack resulting from an immediate response to stimuli in adverse environmental conditions such as low visibility and surf, or in the presence of other sharks or prey such as seals, i.e. the shark must react quickly or risk missing an opportunity to feed or defend itself. The shark usually realises that it has made a mistake and thus ends the confrontation. In light of the millions of humans encountered or detected by sharks without incident, attacks due to mistaken identity that are not caused by poor environmental conditions or the presence of competitors or regular prey may in fact be very rare.
Premeditated (PRE): Methodical and deliberate attack preceded by observation or prolonged stalking, and sometimes a threat display or bumping. The shark sees a target and means to bite or slash in order to investigate, feed (predatory), or fight off a competitor or potential aggressor. Even shark species considered harmless to humans may bite when an object of interest, including a food source, is threatened
Unlike a hit and run case of mistaken identity, the shark may attack repeatedly. Where environmental conditions do not hamper the shark’s vision or other senses, the shark may bite to explore potential prey after a period of observation. Many deliberate bites on humans may in fact be of an investigative nature, which has led some to avoid describing these events as attacks.
Defensive (DF) : The shark bites someone or something that it perceives as an aggressor. Even shark species considered harmless to humans may bite when provoked or threatened, i.e. touched, grabbed, chased, speared, or its movements impeded.
The following are not attacks since no violent action takes place.
Scavenging (SC): Shark consumes a dead body resulting from a shipwreck, drowning or other circumstances.
A shark stalking (ST) people without confrontation is best described as an incident. Although such events do not always result in physical contact, they nonetheless present valuable insight into shark behaviour and risk assessment. Informative cases that could have led to confrontation are included in the Canadian Shark Attack Registry.