It doesn't look it, but this pool is about 6 metres deep. This is low tide. The ocean has to flow around the bouldwer at the back of the photo, and therefore makes this a safe place to swim at high tide because there are no strong currents or rips with the outgoing tide.
And this is a great chasm - the limestone walls are 10-15metres high, and the one on the right angles over the pool. The sun only shines in the pool for a short period each day.
Plus, there is a lot of freshwater runoff here (you can actually see it running out of the limestone at one place) and it sits on top of the seawater in the chasm. If you dive down to the bottom and then float back up you realise exactly how cold the freshwater really is!
