There isn't much life in the Antarctic. Because the continent is almost entirely covered by ice and snow, there's no real room for plants to grow. There are a few mosses and grasses that survive in the harsh conditions, and two flowering plants. Otherwise, plant-life is nearly nonexistent on land.
The water is a different question: Phytoplankton are able to survive in the cold waters, and get their energy from the sun. Krill eat the phytoplankton, and apart from some zooplankton and bottom-dwelling creatures, that's basically the summary of herbivorous Antarctic creatures; everything else is a predator.
Here's a quick overview of four of the most prolific hunters on Earth's southernmost continent:
There are four types of seals that live in the waters surrounding Antarctica: leopard, crabeater, Weddell and southern elephant. All seals are fairly slow predators that hunt by waiting in places their prey is likely to appear. Most of them are unlikely to pay humans much mind at all - except for the leopard seal.
This seal, named for it's characteristic spots, has been know to become aggressive with humans in small boats. They're fierce predators and are perfectly happy to eat anything. Although they don't attack humans often, it's best to give leopard seals a wide berth.
During the summer, antarctic waters are full of many different types of whales looking to eat fish, squid, penguins and plankton. Killers whales are one of the species travelers might be able to spot on their trip. These are the most aggressive and ambitious hunters, as their sights are set on seals, sea birds and other whales. They're perfectly capable of taking down creatures that are much larger than they are, provided they hunt in groups.
Despite being aggressive toward other wildlife, killer whales aren't known for attacking humans in nature. Some killer whales in captivity have attacked their trainers, but generally speaking, humans aren't at any particular risk around these creatures.
Other whale species that travel south for the summer include humpback, orca and the largest animal on earth, the blue whale.
The world's favorite awkward antarctic creature, penguins mostly eat krill and very small fish. They spend most of their time in the water, but usually come on land to mate and raise their chicks.
Although antarctic penguins don't think of humans as a threat or a meal, it's still best to exercise caution when around them. They're not shy around people, and may come right up to you - still, they can and do bite, so it's wise to treat them the way you would any other wild animal.
Antarctica's only true land predators fall solidly under the "creepy-crawly" category. These tiny bugs are fascinating because they're the only creatures that can survive on Antarctica's surface. They handle the winter by going into hibernation - they stand perfectly still, and their blood works to keep them from freezing. This mechanism allows them to make it through to summer, when they get back to eating the smaller bugs.