The HMAS Brisbane bow gun.
The HMAS Brisbane bow gun. Nigel Marsh

IN DEEP: Strenuous day spent in water

SCUBA diving can be a strenuous sport, particularly if the diving is conducted in the open sea.

Divers occasionally have to put up with strong currents, as well as waves caused by local winds.

Diving in a river or lake can be far less strenuous but divers can still be tired after a day in the water.

As well as the local environmental conditions, a diver's fitness will be tested on every dive.

The fitter the diver, the less tired the diver will be at the end of the day.

Diving equipment - especially out of the water - can be heavy and occasionally cumbersome.

Getting in and out of the water wearing the equipment can be challenging in rough seas.

Divers exploring deep wrecks carry extra dive cylinders for safety.

Dive cylinders can weigh more than 10kg each.

Those divers who breathe Nitrox, which has a higher percentage of oxygen, say they feel less tired after a day of diving.

Not only do they not get as tired as divers breathing normal air, they are less prone to getting decompression sickness.

Divers who stay fit and dive within their limitations should always enjoy their time underwater.