I dove below the Falls a few years back, on the East side just off the road. My log book indicates a depth of 42'. Water temp was 71F late June. Saw 2-3 fish (Bass?). What I recall about Bala was the ripping current just off shore, from the falls. First dive I was about five feet off the bottom and got swept downstream, went to the West side and worked my way back up toward the road, then East back across the current to the put-in site. To get back to shore, went to bottom and went hand-over-hand in current to avoid being swept away.
Second dive was much better. Got in, went to bottom and crossed over current (about a 15m stretch) hand-over-hand and then dove on other side without difficulty (no current).
I would do it again. Nothing spectacular, but it makes you think of the conditions, and what you need to do to accomplish a successful dive.
Shawn