In early summer sea ice of around 1.5 m thick covers most of the bays around Casey.
To access the water we therefore need to dig entry and exit holes through the ice. We use a small commercial excavator (Avant) with a purpose-built auger bit that drills a 90 cm diameter hole through the ice in around 30 minutes. A system of three partially overlapping holes creates an ideal dive entry/exit point.
Drilling one of the holes through only half of the thickness of ice provides a step/seat for divers which greatly assists entry and exit from the water. A secondary dive hole is drilled approximately 20 m away from the main hole as an emergency exit point.
Once established, dive holes remain open throughout the season (or at least until the sea ice breaks up and floats away).
Regular maintenance visits are necessary as unused dive holes may freeze overnight to a depth of several centimetres. Later in summer when the sea ice breaks out, diving is either conducted from the ice edge, from 6 m inflatable boats or from the AAD's dive work boat, the Pagadroma.