Figure 31. (A) Drilling core 4 at Grecian Rocks (Fig. 22B) in about 3 m of water. The hydraulic drill can be used both under water and on land (e.g., drilling ancient reefs at Scorpion and Muleshoe Mounds in New Mexico, Ancient Reefs; Shinn et al., 1983). An aluminum tripod supports the drill and drill string of core barrels and assures a vertical core. Each core barrel is 1.5 m (5 ft) long and recovers a core 5.08 cm (2 in.) in diameter. Equipment is lifted to the surface by attaching and inflating an airbag (not shown) with air from a diver's tank. (B) Drilling core 7 at Grecian Rocks in about 8 m of water. Note the difference in bottom habitats at the two drill sites (hardbottom and sand, respectively). Compare water and core depths and bottom habitats in the cross section (Fig. 32).