The concept of grounding is central to yoga, as are the forces at work at the meeting points between body and floor. Transferring a yoga session to the medium of water alters such parameters.
"Water envelops and supports you. It changes your perception of your body. Buoyancy replaces ground resistance and enables you to do things with your body that you cannot on dry land," says Annali Har-Tal, who teaches hydro-yoga, a water-born form of the ancient Indian health regime.
The water temperature in the shoulder-deep Dag Hazahav therapeutic pool near Kibbutz Sdot Yam south of Caesarea is maintained at a steady 33 Celsius.
"Warm water is therapy in itself. The properties of water affect both the body and emotions," Har-Tal explains as the evening's session begins.
We start by adjusting our breath to the fluidity of our surroundings, then slowly begin to explore the possibilities. It takes a few minutes to learn how to balance while adopting an asana, or posture. Many exercises involve the use of rubber floats as a counterbalance.
As the sun sets over the nearby Mediterranean, turquoise hues reflect in the rippling water surface.
"Water gives the illusion of softening resistance, but in fact has the opposite effect. Your body is working hard to maintain these postures," Har-Tal points out as her students struggle in slow motion.
Forget about sun salutations and cobras - movements in the water are constrained to an upright position, and heads remain dry throughout the hour-long session.
Any proper yoga session ends with silent meditation. In hydro-yoga, this involves lying on one's back with rubber floats propping up knees, torso and head as the water laps up stored tension from a long day's work.
"This approach appears to be particularly advantageous for people with movement limitations, such as chronic backache sufferers who cannot carry their own weight. In water, they don't have the same difficulty of movement," Har-Tal adds.
Not that hydro-yoga is ineffective for the already healthy.
"Some people simply love to be in water, and find the combination of yoga and water perfect for them.
"In water, everyone looks the same. You cannot see who limps, is pregnant or overweight. There is no way to watch what others are doing and compare yourself with them."
HAR-TAL, 36, is familiar with physical limitations. She underwent three serious operations between ages 18 and 29.
"A part of my lung was removed. For a year I was at home, linked to tubes. It was a long rehabilitation, during which I found that yoga and homeopathy helped my physical recovery."
As a teenager, she was an outstanding swimmer and accomplished gymnast. She later trained at the Wingate sports institute to become a sports therapist - a physiotherapist who specializes in sports injuries.
"I was a volunteer hydro-therapist at Tel Hashomer hospital for a year. During that time I increasingly incorporated yoga postures, breathing and exercise techniques into my treatments. The positive feedback and tangible results encouraged me to explore this avenue further."
In time, she evolved a systematic approach, and dubbed it "hydro-yoga." Har-Tal makes no bombastic declarations about inventing a revolutionary new fitness regime.
"I'm discovering more about this tool as I develop. It brings yoga to those who cannot practice yoga. Hydro-yoga is growing slowly, at its own pace. I have patience. Everything happens when it's meant to. I still see myself at the beginning of the path - there is so much more to be learned."
She organized her first hydro-yoga class last winter.
"It was time to jump into the water," she chuckles.
A certified yoga teacher, sports therapist, weight room instructor, hydro-therapist and kinesiologist, Har-Tal says that she sought a vocation in rehabilitation, combining her connection with yoga with Western and alternative knowledge of biomechanics.
She is an adherent of the vinyasa school of yoga, whose breath-synchronized flowing sequences of poses build strength and flexibility.
"I used to be a very rational person who wanted everything fast. Vinyasa is a gradual, progressive process based on 'internal listening.' The idea is to bring yoga to the person - not the person to yoga - and suit the session to the individual. I try to stay within these guidelines."
Four times a week, Har-Tal conducts vinyasa yoga sessions for small groups of up to eight students in the studio behind her pastoral Pardess Hanna home. One of the groups comprises children under six.
She also manages fitness activities at an elderly people's center in Pardess Hanna.
"I work with people who recognize the therapeutic value of yoga. The option of water adds a further dimension."
For further information, visit www.hydroyoga.com.