There are many locations in national and marine parks where you might choose to swim. If they are shown on this website then you should be able to swim in comparative safety, depending on conditions at the time. You should also be able to access the water without damaging vulnerable riverbanks.
Plunging into cool fresh water on a hot day may be refreshing but that does not mean you should jump straight in – the risks may not be easy to see. Please also note that most beaches in parks are not patrolled and life-saving help may not be available.
Even on the hottest of days, water in shaded pools or flowing rivers can be icy cold and lead to cramping or shock. Clear water will not be as deep as it appears. If you can't see the bottom, then you can't see how deep it is and if there are any submerged hazards such as rocks or fallen trees or tree branches. If there are trees around, there are likely to be limbs in the water. Flood waters can contain submerged debris and entanglement hazards.
Do not make or use rope swings. Landing on the bank, rocks or other swimmers can result in serious injury or drowning. Trees and their limbs can also break without warning.
Climbing cliffs or rocks and jumping into the water below is called 'Tombstoning' and has resulted in extremely serious injuries and deaths. The name indicates how dangerous this activity is. Do not do it.
Also see the Department of Health's tips for healthy swimming.