Don't swim in champoeg park it's not safe
The portion of the river by the park explicitly states "no swimming." There is a dock where you can fish and put down a boat, but swimming is prohibited. You can drive about 10 miles from the park to Knight's Bridge park where there is access to a calm and swimmable area of the Mollala river.
The river has hard to read and changeable currents, and is consistently strong. There is a fair amount of timber hidden in the water, and it is known to be rather contaminated. If you chose to swim in the river, I highly recommend a shower ASAP afterwards. There have been numerous studies done of the water, and locals joke about catching three eyed fish 😅 All this being said, it can be a good location to relax. When the temperature spikes, just be aware of the increased risk of drowning due to shock. This river remains very cold year round.
Thanks! Your answer is awaiting moderation.