The sea ice edge was right at Cape Royds (continuous sea ice covered the ocean south of the Cape, open water prevailed north of the Cape). A seal was basking on the ice right next to the penguins. The penguins gave it a respectful berth, but didn't seem too concerned. A group of about 20 gathered on the verge of going in, waited a while and then all went in as fast as they could. I've seen videos and heard of this behavior before, but it was really neat to see it in person.