If you have to kick yourself up to maintain your depth, you are wasting energy by carrying weight with your fins and by presenting a larger frontal area to the water. Water resistance increases exponentially with speed. Swimming twice as fast requires four times as much energy. So all your movements, not just swimming, should be in slow motion. Kick within your slipstream.
Wider kicks increase drag.
It used to be said that large, slow kicks were more efficient than short, fast ones, but this is not necessarily true. Keep your fins within your slipstream and, if you have to go faster, increase the frequency of your kicks, not their size. Use efficient fins. Some fins deliver more thrust for a given effort than others. See past ScubaLab tests.