Although I could find very little information on the place, I did find a few articles.
The Ototoka Stream feeds what was once a community swimming pool known as
William Birch Pool.
It was built in the 1934 and used by Maxwell School, nearby, according to this site.
Since it wasn't easy to get to the ocean, the Pool became a public place for swimming.
After falling into disrepair, it was filled in with dirt and then eventually restored according to this article with public toilets installed at the entrance gate.
As we sat on a bench eating our lunch, I could imagine the activity this place saw at the height of its popularity with moms in their modest suits watching young ones in the shallow end and older children jumping off the diving board at the other end.
It seems that the water quality is the main reason it isn't maintained.
It's easy to see why it was a popular place and, even though I never saw it in its heyday,
I feel quite sad that it sits unused.