Common seals (harbor seals) are known to enter estuaries and freshwater rivers in pursuit of their prey. Colonies of common seals live in some lakes, such as seals of Iliamna Lake, Alaska, trapped there a long time ago. There is also a subspecies called the Ungava seal (Phoca vitulina mellonae) that comprises less than 300 individuals landlocked in the fresh water of Lacs des Loups Marins, Petit Lac de Loups Marins, and Lac Bourdel in northern Quebec.
- Edward C M Parsons; Parsons, ECM; Bauer, A (2013). An Introduction to Marine Mammal Biology and Conservation. Jones & Bartlett. p. 118. ISBN 978-0-7637-8344-0.
- "Harbor seal pups swim 60 miles inland in Maine", Portland Press-Herald, June 29, 2011.
- "Resident Harbor Seals (Phoca vitulina) in Iliamna Lake, Alaska: Summer Diet and Partial Consumption of Adult Sockeye Salmon (Oncorhynchus nerka)", Aquatic Mammals, July 2008.
- Turpin, Ben (23 April 2008). "Freshwater seals of Iliamna Lake photographed". Scott Dickerson Blog. Scott Dickerson photography. Retrieved 16 July 2010. CS1 maint: discouraged parameter (link)
- Smith, Richard J.; Cox, Tara M.; Westgate, Andrew J. (17 Jan 2006). "MOVEMENTS OF HARBOR SEALS (PHOCA VITULINA MELLONAE) IN LACS DES LOUPS MARINS, QUEBEC". Marine Mammal Science. 22 (2): 485. doi:10.1111/j.1748-7692.2006.00024.x. Archived from the original on 5 January 2013. Retrieved 16 July 2010. CS1 maint: discouraged parameter (link)