- the study of support systems in wetlands such as the interactions between water and wildlife habitats
- Freewater, P. 2003. Hydro-Ecology - A Framework for Estuarine Research. NSW Coastal Conference proceedings, pp 72-80.
- Freewater, P. 2004. Hydro-Ecology: A Framework for Estuarine Research and Management. Doctoral Thesis (Science). University of Technology, Sydney