Buying guide: accessories (knife, DSMB, weights, light)

In short

A few simple accessories complete your equipment: a tool to free yourself from a line, a DSMB to be seen at the surface, suitable weights, a light and, depending on the dive, a compass, a whistle or a spare mask. They are inexpensive but only useful if you take them on every dive, always stowed in the same place, and if you know how to use them. The safety accessories guide details how to use them.

Why it matters

A fishing line, surfacing far from the boat or a drop in visibility happen without warning. A well-chosen and well-stowed accessory turns these situations into simple incidents. Conversely, an accessory that dangles or snags becomes a problem in itself.

Knife and line cutter

Type	Advantages	Disadvantages
Line cutter (protected hook blade)	Cuts lines and nets with one hand, no risk of injury, compact	Only cuts line
Small short-bladed knife	Versatile, attaches to the BCD or harness	Blade to protect and rinse
Large calf knife	Robust	Bulky, hard to reach, snags; of little use in recreational diving
Diving shears	Very effective on lines and ropes	Less robust, to rinse carefully

• Attach the tool on your upper body (BCD, harness, waist strap), reachable with both hands.
• Prefer stainless steel or titanium, with a sheath that holds the blade without a fragile button.
• Check the local regulations on carrying and transporting blades.

DSMB and reel

• Delayed surface marker buoy (DSMB): bright colour (orange, yellow), long enough (at least about 1 m) to be seen from afar, with an overpressure valve and an inflation system suited to your training.
• Reel or spool: a spool is compact and simple; a ratchet reel is more practical for long lengths. Carry more line than the depth of your stops.
• A closed DSMB stays inflated at the surface even when knocked flat by the swell.

Weights

System	Advantages	Disadvantages
Weight belt	Simple, affordable, can be dropped with one hand	Can twist or slip; puts load on the lower back
Pocket belt (soft shot weights)	More comfortable, does not hurt	Pockets wear out; bulkier
Integrated weights in the BCD	No more belt, weight on the BCD	Check the release; the distribution changes your trim
Cylinder or backplate weights	Adjust trim without being dropped	Not ditchable: complete them with ditchable weights

Buy weights in small increments (500 g to 2 kg) for fine adjustment; the weighting guide explains how to find the right amount.

Light

• Primary light: wide beam for night diving, narrow beam for wrecks and caverns; burn time longer than the dive with a margin.
• Backup light: small, reliable, always in a pocket for night or wreck diving.
• Battery: rechargeable (practical) or disposable batteries (easy to find when travelling); check the rules for lithium batteries on flights.
• For photo and video, choose dedicated lighting (see the underwater camera buying guide).

Compass, whistle and small accessories

• Wrist or console compass, readable and damped; some dive computers have a digital compass.
• Whistle or audible signalling device attached to the inflator hose, to be heard at the surface.
• A spare mask folded in a pocket, a slate to communicate, clips to attach accessories so they do not dangle.

Some manufacturers

Non-exhaustive list, in alphabetical order, with no ranking and no sponsored or affiliate links. Most general manufacturers offer these accessories; check the current range on their website.

Manufacturer	Official website	Range
Apeks	apeksdiving.com	Technical accessories
Aqualung	aqualung.com	Generalist
Beuchat	beuchat.fr	Generalist
Cressi	cressi.com	Generalist
Halcyon	halcyon.net	Lights, DSMBs, reels
Mares	mares.com	Generalist
Scubapro	scubapro.com	Generalist
Seac	seacsub.com	Generalist
Tusa	tusa.com	Generalist

Key takeaways

• A line cutter or small knife on your upper body, reachable with both hands.
• A brightly coloured DSMB, with a reel or spool of sufficient length.
• Weights in small increments to fine-tune your weighting; part of the weight must remain ditchable.
• A primary light and a backup light for night and wreck dives.
• Each accessory has its place and comes on every dive.

Further reading

The guides on safety accessories, weighting, navigation and surface communication explain how to use this equipment. Practise deploying the DSMB with your instructor.