Diving is like mountaineering. The top of Everest is some ten times higher than the hills in the Lake District, but the risk of climbing Everest is far more than ten times greater than the risk of a ramble in the Lakes. The risk of climbing increases exponentially with altitude. There are physiological problems such as low partial pressures of oxygen. There is the unexpected avalanche.
Mountaineers know that survival involves an element of chance.
To push the limits you must be better prepared, more experienced and fitter, but you also have to be luckier.