In the past, UK Cormorants tended to breed on coastal cliffs and offshore islands, but might visit inland rivers and lakes to feed in wintertime. Increasingly they now also breed at inland sites. (One theory is that the inland breeding birds are actually a sub-species that has spread from continental Europe.)
Cormorants are primarily fish eaters which they catch by diving and using their powerful back feet to propel themselves along. Successful fishing is a hard skill to learn. Young birds tend to need much more time than adults to feed themselves – and for the first few months of their lives the adults will also feed them. But by their first wintertime they are on their own (with shorter days and less time to fish). It is estimated that 90% of young birds perish before they are old enough to breed.
Cormorants, and their near relatives Shags, have specially adapted feathers that are ‘dense’ near the body and ‘loose’ at the outside. The outer ‘loose’ feather gets wet when they dive which helps reduce buoyancy. But they need to dry out when they have finished fishing to keep warm. That is why you see them spreading their wings in the sun!