Be safe be seen - swimmers, snorkellers, divers, spearfishers and boaties

Lookout! Issue 29, August 2013

Imagine you are in a speedboat cruising more than 200 metres from the shore, when you see a small blue and white flag – or a red flag with a diagonal white stripe - at water level in the distance.
ALFA flag
It is recommended that spearfishers and free divers tow a float displaying an ‘A’ flag.
Maritime New Zealand ©2020

As a skipper, how would you react? If you do nothing, and keep moving at speed, you may be lucky, and end up with nothing more unpleasant than an irate diver directing hand signals of a less than complimentary nature in your direction. But your luck (and the diver’s) may have run out and the worst could happen – you could be disentangling a diver from your propeller and dealing with the potentially tragic consequences.

Under New Zealand law, divers must use the blue and white letter ‘A’ or alfa flag on their dive vessel to signal diving is being carried out in the area. But as many divers may be international visitors, use of the ‘diver down’ flag (red with a diagonal white stripe (as used, for example, in the USA and Italy)) is also increasingly common.

In reality, skippers seeing any kind of float on the surface, marked in any way, should use extreme caution.

Accidents involving swimmers, spearfishers and snorkellers being struck by powered craft can result in serious injury or death. And injuries caused by propeller strike are almost always serious.

Because there is very little a person in the water can do to avoid a boat, skippers need to be vigilant and aware of any person in the water, regardless of what activity they are undertaking. People in the water also need to do everything they can to be visible to skippers in boats.

As the number of people involved in recreational water use increases annually, so does the danger to swimmers and divers from vessels travelling at high speed.

Maritime Rules

Maritime rules place a range of obligations on vessel skippers and divers:

  • Vessels and skippers are required to keep a proper lookout at all times. This includes actively looking for persons in the water. A high level of vigilance is required, especially when operating close to the shore, where swimmers and divers are likely to be encountered.
  • Vessels are required to proceed at a safe speed. The likelihood of persons in the water should always be considered when determining a safe speed.
  • An ‘A’ flag (the letter flag A (alfa) under the International Code of Signals) must be displayed from every vessel from which dive operations are taking place. It means ‘I have a diver down; keep well clear at slow speed’.
  • Vessels are not permitted to operate in excess of 5 knots within 200 metres of a vessel or raft displaying an ‘A’ flag.
  • Vessels are prohibited from operating in excess of 5 knots within 200 metres of the shore. Consequently swimmers and divers who are within 200 metres of the shore can expect protection from vessels operating at higher speeds.
  • Vessels are required to keep 50 metres from other vessels or persons in the water if exceeding 5 knots.

MNZ has investigated a number of accidents where serious harm has been caused to swimmers, spearfishers and divers by vessels operating in excess of 5 knots within 200 metres of the shore. Victims of these accidents have suffered serious injuries and in some cases have been killed.

In addition to complying with the maritime rules, it is recommended that the following points be followed to ensure the safety of persons in the water:

Safety for vessels

  • The responsibility to keep clear of swimmers and divers lies with the vessel.
  • Keep a lookout for swimmers and divers at all times, especially when operating within 200 metres of the shore.
  • There is no legal requirement for divers not accompanied by a vessel to display any flag, although many now tow ‘A’ flags on floats, or the red and white diver down flag.
  • Swimmers and divers can be encountered well offshore. They can be difficult to see, especially in choppy conditions or in bad light.
  • Vessels should be especially vigilant when operating near beaches in high population areas, where swimmers are likely to be encountered out to or beyond 200 metres from shore.

For dive vessels

  • When divers are swimming from your vessel, you are required to display an ‘A’ flag of at least 600 x 600mm. The flag must be visible to other vessels at a distance greater than 200 metres. Consider a larger dimension flag to ensure maximum visibility of the dive operation in question.
  • In calm conditions, it is recommended a rigid flag system be used so the flag will be visible to vessels approaching from different directions.
  • Carry a sound device on board to alert other vessels of the presence divers.
  • Dive vessels should ensure that their vessel remains at least within 200 metres of where divers are positioned in the water.
  • Avoid conducting dive operations in areas of high traffic.
  • If you intend operating your vessel, be aware at all times of the location of your divers.

Safety for swimmers, spearfishers and divers

  • Swimmers are advised to wear a bright coloured swim cap and swim within 200 metres of the shore.
  • Avoid swimming in areas of high traffic, for example headlands, narrow channels or entrances.
  • Avoid swimming in situations where it will be difficult for vessels to see you, for example where there is reduced visibility or choppy conditions.
  • It is recommended that spearfishers and free divers tow a float displaying an ‘A’ flag. These can be purchased from most dive shops.
  • When practicable and when not accompanied by a vessel displaying an ‘A’ flag, it is recommended that a static float with an ‘A’ flag be anchored where dive operations are taking place.
  • Increasingly, spearfishers are diving into ‘boil ups’ a considerable distance from the shore to spear fish.
    • In these situations, other vessels are often unaware of their presence and will enter such areas to engage in fishing operations themselves. It is essential that an ‘A’ flag be displayed from the dive vessel and by the diver if they are venturing any distance from the vessel.
  • Where a greater degree of visibility for an ‘A’ flag is deemed prudent, consideration should be given to a dan buoy rigged with an ‘A’ flag. This would enable a larger flag than those commonly found on most floats.
    • The flag can be displayed at a higher level, making it more visible to other vessels.
  • Spearfishers should consider diving in pairs with one person remaining on the surface to keep a lookout for vessels that may present a hazard.


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