Complex sentence: The Halliwick Concept was originally developed by fluid mechanics engineer James McMillan in the late 1940s and 1950s, at the Halliwick School for Girls with Disabilities in London, to teach physically disabled people independence in water by developing sense of balance (equilibrioception) and core stability.
Split into simpler sentences: The Halliwick Concept was originally developed by fluid mechanics engineer James McMillan in the late 1940s and 1950s, at the Halliwick School for Girls with Disabilities in London, to teach physically disabled people independence in water. Based on fluid mechanics, McMillan developed teaching and therapeutic approaches concerning physical properties of water and motor control as they relate to sense of balance (equilibrioception) and core stability.