gdude,
Here is my opinion. I think you should save the proper ventilating breathup for all but dives you know you are going extra deep or long on. The main thing ventilating does is decrease CO2. If you have had proper time to recover from your previous dive, you should already be close to being 100% oxygenated.
The point of this is CO2 build up is the primary trigger for the need to breath. In other words pain. If you skip the ventilation you’re not putting yourself in any greater risk. In fact you might even be safer, because the signal to get back to the surface and breath is going to be better.
The other thing that needs to be considered when spearfishing is the dive response or more accurately the CO2 tolerance you get. Competition freedivers don’t do the number of dives a lot spearfishers do. If you have been spearfishing 1 ½ hours and done 25 dives, your dive response and CO2 tolerance may be really high.
Part of doing multiple breathholds is the increasing CO2 tolerance you get. This is why when you do statics it seems to get easier and easier with the more you do because the signal to breath from CO2 becomes less. They may feel like they are getting easier, but after a number (approximately 3-6) your O2% is falling faster than on the earlier holds. In other words you feel like it’s getting easier, but in reality your getting closer and closer to a blackout.
For this reason some spearos don’t believe in doing any ventilations. But the main point is that after you have done several dives don’t use feeling good as an excuse to push your limits. Realize part of feeling good is probably the CO2 tolerance you have built up and not an increase in ability.
So when you get back to the surface from a dive, breath off the CO2 and then concentrate on breathing with the lower lungs using the diaphragm and slowing your heart. When you see a fish you want to dive for, take a big breath and go.
don