What to Carry Underwater: The Gear That Actually Matters
Your BCD, reg, mask, fins, wetsuit, computer — those are assumed. This post is about what you carry beyond that. The stuff that lives in your pockets, clipped to your BCD, or coiled on a reel. The gear that most casual divers skip and experienced divers never leave home without.
None of this is exotic. All of it has solved a real problem at some point.
Flashlight
Always. Even in clear, shallow, daylit water.
A dive light lets you look inside crevices, under ledges, and into holes where the interesting things actually live. It also lets you signal your buddy, communicate when the vis drops, and illuminate your gauges and slate in low light.
Get a light that clips to your BCD or fits in a pocket without rattling around. A backup light isn't a bad idea either — small, cheap, and it's there if the primary dies.
Don't cheap out on the seal. A flashlight that leaks at 60 feet is useless.
Knife or Shears
This is a safety tool, not a weapon. The purpose is entanglement — fishing line, kelp, ghost nets, stray monofilament. You can get into a line problem faster than you'd expect and you need to be able to cut your way out without panicking.
I carry shears (like trauma scissors) over a traditional dive knife because they cut line and monofilament more effectively and don't require the same angle to use. A knife works too. Either way, it needs to be accessible — not clipped somewhere you can't reach with your other hand.
Practice retrieving it before you need it. Muscle memory matters when you're tangled.
Whistle or Dive Alert
A whistle is the minimum. The Dive Alert is better.
The Dive Alert attaches to your BCD inflator hose and uses compressed air from your tank to produce a loud sound at the surface. It is significantly louder than a whistle and doesn't require you to blow into anything while you're trying to tread water, inflate your BCD, and wave down a boat at the same time.
If you're diving anywhere with boat traffic, surface currents, or open water entries and exits — the Dive Alert is worth having. Boats are loud. Whistle range is short. This closes the gap.
Surface Marker Buoy — SMB
A high-visibility surface marker buoy is how you tell boats and your surface support where you are when you come up. It goes up before you do.
The SMB should be brightly colored — safety orange or yellow. It should be big enough to see from a distance. And it needs a reel or spool so you can deploy it from depth without surfacing first.
Reel vs. spool — a reel gives you more line and is more versatile for navigation and wreck/cave diving. A simple spool is smaller and works fine for most recreational deployment situations. Pick based on what you're doing.
Practice deploying your SMB underwater before you're in a situation where you need it fast. It involves inflating the tube while managing the reel and staying neutral — it's not hard, but the first time shouldn't be in a real situation.
Submersible Emergency Light
A small strobe or flashing emergency light that works underwater and at the surface. These clip to your BCD and can run for hours on a battery.
The purpose: if you surface in low light, at night, or in choppy conditions where your SMB might not be visible — a flashing light is seen from much farther away. It also helps your buddy track you underwater if you get separated.
They're inexpensive, small, and easy to forget about until the moment you need one.
Dive Slate or Wrist Slate
Hand signals cover the basics. A slate covers everything else.
When you need to communicate something specific — a compass heading, a plan change, a depth limit, a question — a slate lets you write it. Wrist slates strap to your forearm and are always accessible. They come with a pencil that writes underwater on the plastic surface and erases when you wipe it.
Use it to write your dive plan before you go in so your buddy can read it. Use it to communicate changes. Use it to note something you want to look up after the dive — a species, a depth, a time.
It sounds low-tech. It's extremely useful.
Optional: Integrated Octopus / BCD Inflator Combo
Some BCDs come with — or can be configured with — an integrated alternate air source built directly into the inflator hose. Instead of a separate dangling octopus, your backup second stage is part of the BCD inflator assembly itself.
The advantages: cleaner profile, one less hose floating around, easier to hand off to a buddy in an emergency because it's right there on your chest.
The tradeoff: you need to know exactly how to deploy it fast. Practice locating and handing it off before you're in the water. If you have to think about where it is during an actual emergency, that's a problem.
Whether it makes sense depends on your BCD — not all of them support it and some implementations are better than others. If your BCD has it or supports it, it's worth considering over a traditional dangling octopus setup.
SpareAir Pony Bottle — For Deeper Dives
A SpareAir is a small, self-contained cylinder with a built-in regulator that clips to your BCD. It holds enough air for a controlled ascent from depth — not a long dive, not a substitute for proper gas planning, but emergency breathing gas if your primary fails at a moment you can't fix fast.
This becomes more relevant the deeper you go. On a shallow recreational dive with your buddy close by, the risk calculation is different. On deeper dives, drift dives, or any scenario where your buddy might not be arm's reach — a SpareAir removes a very specific worst-case risk.
It adds minimal bulk and refills with a standard adapter. The concept is simple: if everything else fails, you have enough air to get up.
Nice to Have: Garmin inReach Mini 2
This one operates on the surface, not underwater — but it belongs on this list because it solves the problem that happens after a dive goes wrong.
The Garmin inReach Mini 3 Plus is a satellite communicator. No cell signal needed — it uses the Iridium satellite network, which means it works anywhere on earth. Open ocean, remote coastline, wherever. Two-way text messaging, SOS with two-way communication to a rescue coordination center, live location sharing, and weather forecasts.
The scenario: you surface in the wrong place. Current took you, vis was bad, you came up somewhere your boat isn't. No cell signal. Your SMB is up but it's getting dark.
The inReach Mini 2 means you can tell someone exactly where you are and get help on the way. That's a different category of safety than anything else on this list.
It's compact enough to clip to your BCD shoulder strap or sit in a pocket, and runs on a subscription plan for satellite messaging. For open water dives, remote locations, or any situation where you're far from shore — it's worth the cost.
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The Full List
Essentials — always:
- • Flashlight
- • Knife or shears (accessible, practiced)
- • Whistle or Dive Alert on your BCD inflator
- • High-vis SMB with reel or spool
- • Submersible emergency strobe
- • Dive slate or wrist slate
Optional upgrades:
- • Integrated octopus / BCD inflator combo
- • SpareAir pony bottle (especially for deeper dives)
- • Garmin inReach Mini 2 (open water, remote, or boat diving)
None of this is heavy. Most of it fits in two BCD pockets. The cost of the full list is low. The value when you need any single item on it is very high.
Carry it. Know how to use it before you're underwater.