Studying sea turtles when they leave coastal areas is a particular challenge for research and conservation. As part of a largescale fish-monitoring programme, we have deployed midwater stereo baited remote underwater video systems (BRUVS, Letessier et al. 2013) at 181 sites around northwestern Australia. From 27 turtle observations, we identified 11 green turtles (Chelonia mydas) around Dirk Hartog Island, west of Shark Bay (April 2012) and three olive ridley turtles (Lepidochelys olivacea) on the Australian shelf of the Timor Sea (September 2012, Fig. 1). Turtle encounter rates were 37 % inside the shallow Dirk Hartog pass (mean depth 11 m) compared with 0 % on the seaward side of the island, and 2.5 % in the Timor Sea (mean depth 113 m). Straight carapace length (SCL) was measured for one olive ridley (70.0 cm, an adult female) and four green turtles (SCL =40.6–89.5 cm). At least two olive ridleys and three greens actively inspected the bait (see electronic supplementary material). Our observations provide novel insights into the animals’ finescale habitat usage within Shark Bay and of hitherto suspected deep foraging grounds along the banks and shoals of the Timor Sea (Whiting et al. 2007), confirming the importance of these