McMurdo sound is covered by seasonal and long-term sea ice. Our dept teaches classes in Sea Ice Safety and Travel, and much research is conducted from camps on the ice (which is usually about 6-14' thick), studying penguins, seals, and marine biology and other marine sciences via dive holes. From 2000 to 2005, a massive ice berg (originally as big as Connecticut) broke off the Ross Ice Shelf and became "stuck" off of Ross Island, blocking currents and causing a massive build-up of sea ice that has led to localized reductions of seal and penguin populations (not to mention great difficulty for the USAP in getting ice-breaker ships to bang out a channel to McMurdo so our annual resupply can get in).