Much of his science is interdisciplinary, merging fish biology, ecology and hydraulics in an attempt to improve the design and operation of river infrastructure for the protection of fish. Research projects have included understanding and mitigating the impacts of barotrauma and fluid shear on fish as they migrate downstream through irrigation and hydropower infrastructure. He has also worked extensively on developing design criteria for screens to prevent the entrainment of fish at irrigation diversions. Craig also coordinates a number of projects assessing the outcomes of river habitat restoration and improving the tidal flushing of estuarine wetlands. He is actively involved in international aid research, leading fish passage projects in the Mekong River Basin and participating in international efforts as a representative of the International Energy Agency Fish and Hydropower Annex. He supervises a number of post graduate students at various universities.