Understand constant weight: deep diving on a rope with fins, no weight change. Sequence, blackout risk, supervision rules and course requirement, with buddy and safety.
What does constant weight mean, and why is it considered the king of disciplines? The honest answer: you dive down a rope with fins and come back up without dropping weight or pulling on the rope. The name describes it: the weight you take down, you bring back up. Behind it lies a lot of control, and a lot of risk.
Science gives clear warnings. A study of 14 competitive freedivers wearing a pulse oximeter at depth found: on dives deeper than 35 metres (average 53 metres), oxygen fell to 58 percent, on shallow dives (average 17 metres) only to 74 percent, though both lasted a similar time [1]. Two freedivers showed severe hypoxia already at depth, and four developed it only after surfacing [1]. In competitions with 38,789 starts, CNF, constant weight without fins, had 2.02 times the risk of loss of consciousness [2].
Important: this guide describes the discipline, not training depths. Without a course, supervision and a safety team, CWT is life-threatening. It explains and motivates, it does not replace a freediving course.
Without training it does not work. In the course you learn technique, safety and rescue. For the dive itself: every attempt has safety, buddy and briefing. Milestone: you attended a course and passed the rescue exercise.
Before depth counts, the basics count: duck dive clean, fin kick even, equalization reliable at a few metres. According to Lindholm and Lundgren, equalization problems are a risk factor of their own and can trigger vertigo [3]. Milestone: you equalize effortlessly in shallow water.
The line is your path and your safety. Weight is chosen so you float at the surface, even with full lungs (see DAN's notes [4]). Milestone: you check that you hover neutrally on the rope.
Start with relaxed breathing, equalize early and often, kick calmly. How deep you go is set by your course and your agreement, not your ambition. In a group you never go deeper than your buddy [4]. Milestone: you reach your planned depth without haste.
The ascent is the most dangerous part: rapid pressure decrease lowers the oxygen pressure in the lungs [1]. DAN calls surfacing the most critical part of a vertical dive, with most problems in the last third [4]. Kick calmly and evenly. Milestone: you ascend without accelerating and without panting.
At the surface breathe calmly, show the OK sign and coordinate with your buddy. Stay awake and focused until your buddy confirms. Milestone: you give the sign clearly and without delay.
Dive with a plan that can also say no. Before the dive decide: depth, turn sign, abort signal. If today the feeling is "heavy", turn around. Competition data show higher incident rates in the no-fins disciplines [2], where the reserve is smaller. You win nothing by ignoring an uneasy feeling. And write two sentences after every dive: what felt easy, what felt tight? After ten entries you see patterns no computer shows.
Deep diving on a rope with fins, under your own power, without changing weight. You leave nothing behind at the bottom and do not pull yourself up the rope.
Course, instructor and your abilities decide. There is no proven ideal value for beginners, so we name no number. Depth grows with experience and supervision.
Because ambient pressure falls and with it the oxygen pressure in the lungs. On dives deeper than 35 metres, oxygen in one study fell much further [1]. DAN calls the surfacing phase the most critical [4].
Yes. Even competitive athletes dive under safety. Without a buddy a blackout in the water can be fatal [4].
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