It’s always astounded me how relatively “shallow “ our knowledge of the sea is and again, I’m equally puzzled, fascinated by how “shallow “ we have to go before things get seriously dangerous. Remember thinking of the Kursk and how it couldn’t be salvaged from 130-150 metres. Then looking across the school playground and thinking that it was the same distance. And wondering how it couldn’t be done. I’ve read some great books too about diving / apnea and as soon as we go below 100m it’s fraught with danger. Seems such a short depth. But then I remember diving into the 12ft deep end at Eccles baths and realised just how fucking hard it is at even that depth to get back up without vomiting your lungs inside out. Fascinating