Swimming in Lake Ginninderra is permitted. Beaches located around the Lake provide signage that should be observed before entering the water.

The lake has a surface area of 1.05 square kilometres (0.41 sq mi) and an average depth of 3.5 metres (11 ft). The water temperature from May to August each year is considered too cold (in and around 11C) to undertake primary contact activities like swimming. In summer months, from mid-November onwards the water temperature is 17C – 21C, though temperature can vary markedly from one part of the lake to another.

When a Beach is closed at Lake Ginninderra it is typically due to high levels of bacteria. Blue-green algae occurs naturally in most ACT water bodies, usually in low numbers and in balance with other aquatic life. Given the right environmental conditions – warm weather, low rainfall, and the right mix of nutrient levels. Bacteria outbreaks can also be the result of recent rainfall which washes things like dog and duck poo into the catchment area. Blue-green algae can rapidly increase to high concentrations that causes deterioration in water quality and pose a threat to public health. As blue-green algae die they can release toxins into the water. These toxins can cause symptoms such as eye or skin irritations, sore throats or gastro-enteritis in humans.

When a Beach is closed for primary contact (which includes whole-body immersion, such as swimming, diving, waterskiing or windsurfing), it may still remain open for secondary contact such as sailing, canoeing or rowing.

The ACT Government provides advice on their website with respect to Lake closures.