The expedition team's instructions come first and they override any photograph you had in mind. You generally stay at least 5 metres from wildlife ashore, with greater distances for some species, behaviours and sites, and South Georgia and the Falklands have their own rules. The sentence worth memorising: a lens, tripod, selfie stick or bag does not let you get closer.
Move slowly and quietly, and never block an animal's route between the colony, the nest, the beach and the water. If wildlife approaches you, stay calm and follow your guide. An animal choosing to come closer isn't permission to touch it.
Never use food, sound, movement or another person to provoke a reaction, and don't use flash where it's prohibited or would disturb an animal. A natural behaviour photograph is worth more than one you engineered, and it looks better too.
Don't leave a marked trail, enter a closed area, block another guest or create a safety problem for a shot.
One last thing worth saying. Antarctica shouldn't be experienced entirely through a screen or a viewfinder. Put the camera down occasionally. The photographs matter and being there matters more.