1. Go Slow
Move slowly...fast, jerky movements increase resistance underwater.
Breath slowly...inhale for around 5 seconds, exhale for around 7 seconds. Get used to breathing slowly and you will not have to count.2. Stay Warm
Diving un-insulated causes your body to release heat into the water. This increases your metabolism and oxygen-burn rates. Wear proper exposure protection depending on the water temp
.3. Reduce Drag
Reduce drag by being properly weighted
and have all gear clipped in and close to your body. Use your fins for movement, keeping your arms mainly at your side or crossed. Using your arms increases resistance in the water.