As a psychologist I understand post-traumatic stress as something that affects the body and mind; the mental, emotional and physical all wrapped up together.  An analogy I often use to explain this when I work with people experiences the after effects of trauma is: if you had ran a marathon your body has been used hard, muscles will be sore, joints inflamed. If you go through traumatic situations the parts of the body that operate for survival and social connection have been used to their limit. Those systems include the emotional reactions and thought processing, and these are all hooked up with the brain, nerves and hormones like adrenaline. When these systems have been working to survive a traumatic event (for some people repeatedly and without respite) they get sore and inflamed too.  On the other hand the systems for growth and development are sidelined in favour of survival; so motivation and pleasure is low or non-existent.  All of these systems need to recover after trauma, just like in physical exertion or injury, sometimes rest and reconnecting with friends and family is enough but sometimes the injury is so much that some “emotional physiotherapy” is needed.  

People will always attempt to regulate these systems.  We select our method of regulation according to what we have seen others use or what we know has worked for us in the past.  When the dysregulation is extreme, as it often is in trauma, then bringing it back to equilibrium is more of a challenge.  Traumatic experiences have an impact on the sensory system, so that normal levels of noise, touch and light in daily living can become both over- and under- stimulating.   Social interaction can be intolerable due to the effort needed to control behaviour to fit the social norms.  Avoidance of situations and people that increase dysregulation is common; as are external methods of regulation such as alcohol, prescription and non-prescription drugs, or sadly, self-harm and thoughts of suicide.  We turn to anything that helps to regulate the unbearable physical and emotional fallout from trauma. These methods are not wrong or bad, in fact people will report them helpful and medication has a place, but they can get in the way of living a meaningful life. Staying home might give respite from intense anxiety, but it also means losing touch with friends, and so suppresses rather than addressing the issue.  Horrible, self-destructive patterns of thought develop and further compound the regulation problem, for example it is hard for mood to improve if you are stuck in a quagmire of negativity, derogation and self-hatred. Trauma leads to disconnection that can lead to losses such as work or relationships, and subsequently damages self-worth.   

There are many activities that can help to re-established regulatory function. One of them is scuba diving.  Why would scuba diving help? We know from the many stories that it does help, but there is little research on the mechanism. I suspect several factors:

• To dive below the surface for an hour or so offers a little bit of escape from the world.   For people suffering the effects of trauma, normal life has become overwhelming; just knowing there is an option for escape without resorting to suicide can bring huge benefits and give people an alternative means of managing distress.
• Underwater there is a reduction in the usual information to the senses, in particular reduced noise and visual stimulation.  This decrease in sensory information can be helpful in soothing an over-stimulated nervous and endocrine (hormones) system.
• Social connection in diving is vital; learning to scuba dive within a supportive instructing team can be the perfect framework to begin to connect with people again.  It also means having something to talk about again, which is essential for people who have disconnected socially due to trauma.
• Learning that you are capable of surviving underwater and have the skills to navigate this world is an undeniable achievement and provides a foundation to start building self-worth again. Learning to dive is about taking an active role in generating change.
• The process of learning a skill means engaging the systems needed for growth (i.e. the reward and motivation systems of the brain as well as the muscles and nerves).  This can lower the activation in the systems built to manage survival. Scuba diving training is particularly helpful in that the learning is across multiple modalities (tactile, auditory and visual) as well as improving physical fitness.
• There are rules. Scuba has rules and procedures that provide certainty and containment when it feels the rest of life has fallen apart. Self-regulation is part of the training, we learn to slow our reactions in order to think and problem solve clearly.  Learning to dive means working within a clearly defined framework with an indisputable rationale for building skills in management of physiological and emotional systems.  There are clear measures based on the mechanical relationship between emotion regulation and desired outcomes (e.g. stay relaxed, conserve air and gain a longer dive); and improvements are therefore made tangible.
• Biological benefits: it may be that the physical effects of pressure have calming effects on the nervous system and body as a whole.  We have various baroreceptors in our bodies which are part of the sensory system and measure pressure.  Anecdotally, divers report the pleasant, calm sensation that comes with depth. 
• Diving means learning to breathe again. In trauma reactions breathing becomes shallow and restricted, learning deep breathing is part of dive training and is often more acceptable to people than a formal relaxation class.
• Being in a new environment is habit-breaking so we can let go of the unhelpful thoughts and behaviour of the surface world to give something else a go, for example allowing some room different thoughts and beliefs; changing the focus of our attention.

One of the major effects of trauma is also that it creates barriers to accessing the very things we need to recover.   Scuba diving has the potential to provide the access to these vital supports when ordinary life is not. It also has some unique therapeutic features that make it appealing to specific groups of people who have experienced trauma.