Shallow macro dives are awesome!!! Some of the best times that I’ve had have been in the shallows with a camera. And by shallow, I’m talking 5-8 meters. Why? Let me go through the reasons:
Long Long Long Dives. Since divers don’t consume air quickly in the shallows (you should know this from your basic open water class), we have more time to shoot. Like 80+ minutes from a single 11.2 Liter aluminum, even more if you’re a tiny person. That’s a lot of photos!!
No Decompression Limit. This is the biggest benefit. Since macro divers have longer dives than most divers, nitrogen saturation and NDL are a bigger issue. But when you’re less than 10 meters deep, it’s impossible to breathe enough nitrogen to run into mandatory decompression. In fact, the entire dive is at a normal decompression depth. This means less surface interval time.
Better Ambient Light. This means you can hunt subjects without a torch. This means that in some cases you don’t even need artificial light for your subject. The picture below of the blenny was taken at 4 meters deep with a low-power fill strobe to add color. However, you can see the background is also not as blue as in deeper dives.
Shorter Swim Times and Smaller Gas Reserves. On shallow dives, it takes less time to swim down to the bottom and then up at the end of the dive. This means more time on the bottom looking for subjects. But more importantly, when you dive deep you need more of an air reserve. Say, from 25 meters deep you might “turn the dive” and start swimming up to the shallows at 80-85 bar so that you get to the safety stop at around 50 bar. Any less doesn’t give you enough gas to deal with emergencies at depth. On a 5 meter dive, “turning the dive” means that you surface. You only need 5 bar (if that) to surface from 5 meters, so you head up at 30 bar: the gas reserve can be a lot smaller. Just be kind to yourself and don’t run completely out of gas: it adds quite a bit of risk if you can’t make it immediately to the surface and it is bad for the cylinder because it could let water inside.
Surface Swims. On a shallow dive, you can save air by doing a surface swim without using your regulator set (protip: a snorkel comes in handy). Because you can see the bottom, you can still navigate.
Extend Your Deep Dives. You can get in a shallow macro dive as part of a deeper dive by simply extending your safety stop if you’re near the bottom. Instead of sitting around motionless for 3 minutes at 5 meters like most people do, try looking around for subjects and snapping photos for 15 minutes or until you get low on air. This comes with a warning: sometimes non-macro-diving divemasters freak out when I surface with only 20 bar of gas. (Hi guys!!) =)
3rd and 4th and Night Dives. Usually when you do 2 deeper dives earlier in the day, it’s safe to do one or two shallow macro dives. Even if you started the day out doing wide-angle, you can take a break, get lunch, reconfigure your camera for macro, and go do a relaxed shallow dive. No stress + no NDL + macro photography = fun!
See you underwater!!!