Until recent history, the Toronto Islands were a very dynamic presence along the shore of Lake Ontario. The unstable ridges of sand, protecting the mouth of the Don River, regularly changed form over the seasons and during intense storms. Over the past century, the construction of wave breaks and armoured shores to stabilize the sand bars, have removed the island’s ability to respond to changing climate conditions such as a rising seasonal high-water. With Sediment, the removal of all shore stabilizing infrastructures on the site, restores processes of erosion and sedimentation, reflecting seasonal and climate trends. This bathing and spa complex was conceived of as an instrument for observing and experiencing flows of wind, water and sand on the island shore. The linear building runs transverse to the ever-changing shoreline where it interrupts counter-clockwise lake flows and becomes a factor of land formation. The experiences of the spa and leisure pools trace the natural forces in operation on the dynamic form of the shore.