Dive Guides

Mild, well-controlled asthma is often compatible with diving under DAN and UHMS guidelines. Here's what "well-controlled" actually means, and why medical clearance matters.

Flying too soon after diving can trigger DCS just like too fast an ascent. Here's where the 12/18/24-hour guidelines actually come from, and why they're minimums, not targets.

Up to 90% of deep-sea animals produce light, and it's evolved independently at least 40 times. Here's the chemistry behind the glow, and why dinoflagellates flash when you disturb them.

Some whales can hold a single breath for nearly 4 hours. Here's how myoglobin, bradycardia, and collapsing lungs make it possible, and why the trick doesn't work for scuba divers.

Divers make up under 5% of unprovoked shark bites despite spending the most time near sharks. Here's what the actual data shows, and why sharks rarely see divers as prey.

Octopuses colour-match reefs in under a tenth of a second, despite being colourblind. Here's how chromatophores, iridophores, and light-sensing skin make it happen.

Fish do get decompression sickness, just from a completely different mechanism than divers. Here's why gills change the physics, and what a swim bladder has to do with it.

Water pulls heat from your body 20-25x faster than air at the same temperature. Here's the physics of thermal conductivity, real hypothermia timelines, and why wetsuits actually work.

Sound travels 4.5x faster underwater, which sounds useful until you realise it destroys your ability to tell which direction it's coming from. Here's the physics behind directionless hearing underwater.

Red disappears within the first few metres of any dive, gone almost entirely by 10 metres. Here's the physics of why water eats colour, and why your brain doesn't notice until you see a photo.

Heart rate, HRV, and skin temperature are now standard features on premium dive computers. Here's what biometric tracking actually does, and what's still hype in 2026's biggest dive tech trend.

"Oxygen tank" is one of diving's most persistent myths. Here's what's actually in your cylinder, and why pure oxygen becomes toxic at just 4-6 metres.

Nitrox extends your bottom time by reducing nitrogen, but it actually shortens your maximum depth. Here's the physics behind enriched air, MOD calculations, and why the trade-off works.

Johannesburg's elevation quietly changes the physics of every dive. Here's why altitude steepens the pressure gradient, shortens no-decompression limits, and why your computer setup actually matters.

The bends happen when nitrogen dissolved in your tissues forms bubbles on ascent. Here's how supersaturation works, what exceeding bottom time actually risks, and why some hits are "undeserved".

Holding your breath while ascending can rupture lung tissue in as little as a metre of depth change. Here's the physics behind pulmonary barotrauma and why the oldest rule in diving still matters most.

A cheap computer and a current one can look identical, but the algorithm underneath decides how much decompression margin you actually have. Here's what really separates budget from premium.

Everything really does look about a third bigger and a quarter closer underwater. Here's the physics behind the illusion, and why it flips at longer range.

Nitrogen narcosis makes divers feel drunk at depth, and it's the leading cause behind more diving errors than most divers realise. Here's what causes it, what it feels like, and how to manage it.

Ear problems are the leading cause of diving injuries, but nearly all are preventable. Here's how to equalise properly, which techniques to try, and when pain means it's time to end the dive.