The water is clear, and the surface matter is simple duckweed, which is harmless and actually good for the water quality.
However, remember this is a watershed pond (as is the case with all the ponds in BC), which means it is fed by surface run-off from the surrounding areas (streets, lawns, etc.). My dogs have been swimming in and drinking it for 10 years, and have never had a problem. Other dogs partake once and occasionally come away with ear, eye, skin or intestinal problems -- although there have never been reports of a serious illness.
The cleanliness of these ponds is very dependent on keeping the park free of feces residue................ so scoop your poop, and pick up any orphans you encounter.