We swim the "Teachlan", which is from Teachbeach to Hanlan's (about 1.5km each way) regularly and notice the extreme difference in water clarity of Teachbeach (Ontario Place) versus Hanlan's (Toronto Island).
Both are safe to swim in, e.g. although Teachbeach / Ontario Place has better (cleaner) e coli count (1.8 versus 29) both of these are safely below the 100 limit.
However, visually speaking, the Teachbeach is much more appealing and at the very least makes for wonderful underwater music videos, underwater exploration, and of course, teaching, learning, research, scientific explorations, and the like.
Let's preserve Teachbeach as a fun playful artistic and scientific space free and open to the public.