If I am correct most people find seals to be rather benign and cute or amusing. It is easy to forget they are serious predators. Leopard seals are certainly an exception to the cute and benign idea.
They are also called sea leopards because they are spotted, swim up to 25 miles per hour and have a mouthful of sharp teeth.
According to Brittanica these seals can top 800 pounds and reach a 12 foot length. They prey on other warm blooded mammals for the most part. Other sources say they eat kril, fish octopuses, penguins and oher seals.
Leopard seals (Hydrurga leptonyx) so far have rarely attacked people. One fatal attack occurred in July, 2003. Researcher Kirsty Brown (Some media outlets say Kristy) was dragged to her death by a leopard seal. A few less dangerous attacks have also occurred. British Antarctic Survey (BAS) protocol requires researchers to exit the water if a leopard seal is spotted.
The seals are fierce but are definitely number two. Orcas are the most lethal predators in Antarctic waters. They prey on leopard seals. As noted recently, they even kill and eat blue whales. Far from sterile, Antarctic waters are teeming with life. Recently, researchers have found vast amounts of life in the cold waters. One discovery was a 92 square mile icefish hatchery. Icefish are a kind of fish specially adapted to life in the deep frigid sea. They even lack hemoglobin in their blood.