Those tiny black spots on the ice berg are Adelie penguins. Leopard seals like to eat adelie penguins, and lurk in the water near their rookeries to catch them. So the adelie penguins have evolved some protective measures against the leopard seal. Firstly, they only enter the water in large groups. Secondly, they swim like crazy to an ice berg (or ice flow) and then ride the ice berg for some hours until they are well clear of the rookery.