They can dive, swim and glide but even the penguins at London Zoo will find it difficult to hide from keepers who have the tricky but essential task of counting every animal in their care.
Some of the world's most endangered species, including rare penguin breeds and two new lion cubs, will be counted for the first time in this year's stocktake.
Macaroni, blackfooted and rockhopper penguins will be among those totted up in their new 1,200 square metre home - the largest penguin pool in the country - along with 752 different species at the zoo.
Adrian Walls, team leader of birds at ZSL London Zoo, said: "We built a very naturalistic environment for the penguins so they can come and go and swim around.
"We work with these birds every day so we know their characteristics and we get to know most of them individually.
"The count does take some time but the penguins have their own individual tags so we can tick them off when we see them."
Once the final figures are collected the data can be shared with zoos worldwide and can be used to help breeding programmes.
Mr Walls added: "Generally speaking we don't ever lose any animals. We monitor them on a daily basis to make sure every animal is happy and healthy."
Armed with clipboards and abacuses, the zookeepers recorded 18,499 animals last year, but since then two ginger-haired Francois langur monkeys and two new lion cubs have been born.
The female cubs, nicknamed Pumpkin and Spook, made their first appearance in their outdoor paddock in November and are beginning to play fight with each other.
There are around 350 Asian lions remaining in the wild and 90 in captivity.
The cubs are living with their mother, Abi, in the lion den and are slowly being introduced to their 28-stone father, Lucifer.
Mark Habben, zoological manager, said: "The lion cubs are probably the most impressive new arrivals and they are on view now which is a very exciting sight.
"The animals that are always harder to monitor are the fish in the aquarium. There is a lot of rock work so it's hard to be able to count everything.
"It can take up to several weeks for zookeepers to complete the final count in the bug house and aquarium."
The stocktake is required as part of ZSL London Zoo's licence.