Whether with bifins or monofins, going down deep requires a perfectly adapted material that will effectively propel you with a minimum of effort.Sufficient power will be required to overcome the positive buoyancy zone at the beginning of the descent and the negative buoyancy zone after taking off from the bottom. However, you don’t need a too hard blade that will consume a lot of energy with each movement. Always a question of balance.For the length in bifins, we will focus on long fins that amplify the movements of the freediver except for the smaller statures who can use a little shorter fins that have a faster activation. In constant weight, probably even more than in other disciplines, it is necessary that the footpocket perfectly transfers energy to the blade with a minimum of loss. However, it must remain comfortable because any discomfort hinders concentration.