One goal of diving is to acquire a slower breathing rate while underwater.
When you first learned to dive you probably had a higher rate of breathing because you may have been anxious and a little stressed during your beginning dives. Over time you develop a calmer attitude and more comfort in the water, resulting in slower breathing.
By having a slower breathing rate, you will be able to maximize your time underwater by extending the amount of time you can get out of a single tank (or whatever your tank configuration).
As long as you are not holding your breath or skip breathing, you are fine. Your body will let you know if you need to breath faster. Enjoy the extra efficiency.
You're close... but you sort of have it 180 degrees out of phase.
A slower breathing rate is - for the most part - a desirable state for scuba divers. However, it is not a "goal" of diving. In fact it should be noted that breathing rate is only one part of the respiratory equation that determines air consumption. The other part is the depth (volume) per breath. A slower breathing rate that is shallow may result in CO2 buildup and/or simply not deliver sufficient O2 to meet the metabolic needs of your body. Neither of these two situations are desirable.
Air (O2) consumption is a DEMAND function which is controlled by the metabolic needs of your body in terms of delivering O2 to your body's cells and removing CO2 that results from metabolic processes. Accordingly, the best approach to reduce air consumption is to reduce your body's DEMAND for O2 delivery and CO2 elimination. There are 13 key "Demand Reduction Strategies" that any and every diver can employ to improve their O2 consumption:
1. Slow down
2. Get more comfortable in the water
3. Slow down
4. Get your weighting fine-tuned
5. Slow down
6. Get your horizontal trim dialed-in
7. Slow down some more
8. Stop swimming with your hands and arms
9. Slow down even more
10. Utilize efficient propulsion techniques
11. Just a little bit slower... please?
12. Streamline your gear
13. Slow down - you're still moving too fast!
Reducing various behaviors, factors, and circumstances that increase your body's metabolic processes - which increases the DEMAND for O2-in/CO2-out - is an appropriate goal. Achieving this goal will result in a decreased respiratory rate and therefor decreased consumption. I know it sounds semantic, but I've found that most students/divers have better results when they get the cause-effect relationship down. Doing so will allow the diver to identify and correct the underlying cause of an elevated respiration rate.
Two fine points to add:
- Sometimes - especially with new divers - an elevated respiration rate is a reaction to anxiety, etc. And yes, that underlying cause should be identified and addressed as well. (See point number 2 above.)
- Within about 10 seconds someone will reply to this post saying "But breathing exercises and yoga-type techniques are shown to reduce anxiety and slow the body's metabolic rate, etc, etc." Fine. However, that's not really any different than what I'm suggesting: the goal is to identify the cause of the elevated breathing rate and addressing THAT. Doing so will result in a reduced breathing rate and improved gas consumption. But I will suggest that - other than in anxiety/panic situations - divers should implement (and probably exhaust) the various DEMAND reduction strategies as the primary focus.