What do you need help with?

We have a concrete pebblecrete pool. We are in Wahroonga. The water level would typically fall below the skimmer box within 2-3 days when the pump is running. There is no visible crack that we can see. Hoping to get some help to work out if there is a leak.

One corner (1Mx1M) of the deck is wobbly. Some "planks" are loose. When pressed, feels like the support beam underneath is gone. Looking for help to fix that part of the deck.