Why a dive computer is so important to freediving and spearfishing

The one thing every spearo and freediver needs is a freedive dive computer, but why?

Why use a dive computer
A dive computer makes breath-hold sports safer, more enjoyable, and helps to improve performance.

Freedivers were some of the first to start using Freedive computers for breath-hold and over time, the training and the safety side of freediving have trickled their way into spearfishing. The need to understand how to dive deeper and safer has become increasingly important to the spearfishing community.

So unless you know a little on breath-hold training, a Freedive computer probably means “nothing” to you, or “nah, waste of time”, “I don’t need it”, or maybe “I have a watch, I can tell the time already”. The reality is, once you know a little bit about the way your body works when holding your breath, they are invaluable.

So here’s some advice on why a dive computer is important as well as a little science behind breath-hold training, and how both work hand and hand.

CO2 and Blackouts
When you hold your breath, your body produces carbon dioxide (CO2). The longer you hold your breath, the more CO2 is produced. Our body is not a fan of CO2, so if you have short surface intervals (time between dives), your CO2 keeps building up. Your dives become shorter and the high CO2 could be one of the contributing factors to a possible Shallow Water Blackout. Basically, you become unconscious underwater (this is by no means what any of us want) and this is where the Freedive computer comes into play - helping you prevent blackouts, and manage yourself and your dives.

Surface intervals are the key thing to help your body lower your CO2 levels. This happens naturally while you are on the surface breathing. Your Freedive watch shows your surface intervals in big clear numbers while on the surface. Most importantly, the longer the surface interval, the lower the amount of CO2 you will have in your body.

The ideal surface interval
Keep in mind that this is a guide only, although we have found this to be good practice. A minimum surface interval should be double your dive time - therefore if your dive time is 60 seconds (1 minute) your surface interval time should be 120 seconds (2 minutes). It is impossible to count this accurately (many have tried), but a quick glance at your wrist will clearly tell you this valuable and necessary information. Even if you have doubled your surface time and you still don’t feel like diving - don’t. Wait longer. Recognise that your body is not yet ready. Some of the deeper dives or longer bottom times require longer surface intervals. You may triple your surface time or wait longer before those longer, deeper dives. The longer the surface time, the more time your body has to reduce the CO2 in your system.

Dive time for recreational use
Your watch will count your dive time. Let’s say you just did a 90-second dive, do not use this time and think “I will stay down on my next dive for the same time”. Make sure you listen to your body, and if you feel like coming up for a breath of air before this time, do so. You’ll probably find it will be close to the previous time anyway. Never stay down by forcing yourself just because your Freedive watch said you had a good dive previously.

Dive time in relation to depth
A good rule of thumb when breath-hold training is trying to stick to 1 meter per second. If it’s a 10-meter dive it should take 10 seconds to get there, and 10 seconds to get back. So you should be aiming for a 20-second dive plus any bottom time. This rule is an easy one to remember, enabling you to be more efficient in the water. Use this rule when spearing.

Some other great features your Freedive watch offers

  • Keeping track of your buddy's dive time (use your surface time as a guide)
  • Depth Alarms - set a depth alarm just in-case you go deeper than expected - ideal for bluewater hunting and equalising at depth (the latter is more used in depth training and Freedive competitions)
  • Stopwatch - perfect for training.
  • Time – keeping track of the day.
  • Back light – Enables you to see your screen in the dark.
  • Depth - How deep you are.
  • Dive Counter - Counts your dive.
  • Dive History/log - Review your dive history.
  • Water temp – Helpful finding some species that prefer certain water temperatures.
  • Training Mode – Some watches have a training mode for breath-hold training.

There we have it. A simple explanation on why you should use a Freedive watch and a couple of simple features can help make some big changes to your diving safety. It is without a doubt that having a watch, some basic techniques, and making good choices, takes the guesswork out of your diving, inevitably creating a more relaxed, fun, and safer dive.

Click here to have a look at the Freedive watches available at Ocean Hunter.

Safe diving everyone.

Written by: Mike Smith, Managing Director, Ocean Hunter Ltd, New Zealand

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