Kaiserwasser is opposite the Vienna International Centre, just across Wagramerstrasse. Water entry is close to the Arcotel. There is very little leisure boat traffic, but it can get crowded.
Gänsehäugel's water is cleaner than Kaiserwasser, but there is a bit more leisure boat traffic; be aware of your surroundings. The entry point can be accessed by a short walk around Kaiserwasser. After crossing the small bridge at the left end, use the sliproad on the right, to enter the water, opposite Gänsehäufel Westrand. From this point, the swimming distance to the south bridge, is about 600 metres.
There is an easy entry and exit though a jetty with stairs, to the right of the Wagramerstrasse bridge over the Alte Donau. We swim past the Strandcafé, Distance to the sailing club is just below 500m. Boat traffic is minimal. This spot, like most Alte Donau spots, gets warm much earlier than Neue Donau.