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The largest predatory animal on earth is the sperm whale. They dive more than 1000 meters deep hunting for food. These animals are named after their huge heads, which make up nearly a third of the total length of their bodies. They have the largest, heaviest brain of any species known to have lived on Earth, weighing up to 9.5 kilos. Scuba diving with sperm whales is a beautiful sight you would never forget where you can admire their furrowed skin and marble-like coloration.

Sea lions are pinnipeds that are easily recognizable by their external ear flaps, cute, pointy nose, long, puffed up chest, and their ability to walk on all fours. Some of the more popular sea lion species are the California sea lion and the Steller sea lion. These fast, agile swimmers can reach up to 30 knots underwater and are very curious about the world around them. In fact, sea lions are not afraid of scuba divers in the least and have been known to buzz right around a group of divers, blow bubbles at them, and even chewing on their snorkels and fins.

The conger eel, also known as the European conger, is distributed throughout the eastern Atlantic Ocean and is particularly present in the Mediterranean Sea. These robust eels are the heaviest marine eel species within the Congridae family and a favorite sighting amongst European divers, growing up to 3m (9.8 ft) in length and 72 kg (159 lb) in weight!

There are nearly 130 different species of marine butterflyfish all living in the tropical waters of the Atlantic, Pacific, and Indian Oceans. These beautiful, small fish are known for swimming in monogamous pairs but can sometimes be seen in large schools. Like their larger cousin, the angelfish, they are a favorite sighting for scuba divers and snorkelers due to their beautiful, bright coloration and striking patterns. Another distinguishing characteristic is the eyespots many species have on their flanks to trick predators, similar to those found on butterfly’s wings.

Scorpionfish are one of the most venomous yet undetectable fish species in the sea. These ambush predators are experts at blending into their environment as they sit and wait patiently on top of the reef for unsuspecting prey to swim by. Ranging in color from dull browns and yellow to bright reds and oranges, scorpionfish perfectly match the surrounding reef and even exhibit feathery fins or skin flaps to better camouflage with neighboring coral.

Flounder is a generalized term for any number of flattened fish species belonging to the families Pleuronectidae, Paralichthyidae, Achiropsettidae, and Bothidae. This unusually shaped fish looks like a flattened oval with the dorsal and anal fins running along the entire length of the body. One of the flounder’s most unusual characteristics is that after just a few days of life, one of its eyes begins to migrate to the opposite side of its head to what eventually becomes the fish’s top side.

One of the most common and widely recognized jellyfish in the world, the moon jellyfish is clearly distinguishable by its clear, round main body with four purplish-white circles at the top of the bell. Although many beach-goers fear jellyfish due to their powerful stings, the moon jelly is one of the few that do not sting humans. Affectionately called the moon jelly, this cnidarian has relatively short tentacles hanging down from its bell’s sides.

Crustaceans encompass a vast array of hard-shelled, mostly aquatic animals such as crabs, lobster, shrimp, prawns, krill, and barnacles. Although woodlice and a few crab species live on land and in freshwater, most crustaceans live in the ocean. They can be found in every ocean habitat from prawns and shrimp swimming freely in the open ocean to barnacles attached to rocks, piers, and even the sides of ships. They will be encountered at every depth from krill, floating near the water’s surface to shrimp-like creatures in the ocean’s deepest trenches. There are 50,000 known species of crustaceans, with more discovered every year.