Marine Life Encyclopedia
From the smallest coral polyp to the largest animal ever to exist, our oceans are home to an extraordinary diversity of life. Explore expert guides written by Irish marine biologist Rowan Byrne.
The ocean's apex predators
Over 500 species of shark patrol the world's oceans — from the mighty great white to the gentle whale shark. Discover their biology, behaviour and vital role in marine ecosystems.
500+
Known species
450M
Years on Earth
Threatened
Conservation status
Giants of the deep
Whales are the largest animals ever to have lived on Earth. From the blue whale's haunting song to the humpback's acrobatic breaches, these cetaceans are among the ocean's most iconic creatures.
90+
Known species
30m
Blue whale length
3,000m
Dive depth
Intelligent social swimmers
Dolphins are among the most intelligent animals on the planet. Living in complex social groups, they communicate, cooperate and play — making them endlessly fascinating to marine scientists.
40+
Known species
60 km/h
Top speed
Up to 60 yrs
Lifespan
Ancient ocean navigators
Sea turtles have roamed the oceans for over 100 million years. These ancient mariners navigate vast distances across open ocean, returning to the same beaches where they were born to lay their eggs.
7
Known species
100M+
Years on Earth
10,000km
Migration range
The ocean's most diverse group
Fish are the most diverse group of vertebrates on Earth, with over 30,000 known species. From tiny gobies to massive ocean sunfish, they inhabit every marine environment from shallow reefs to the deep sea.
30,000+
Known species
8,000m
Deepest found
50%
Of all vertebrates
Architects of the reef
Coral reefs cover less than 1% of the ocean floor yet support around 25% of all marine species. These remarkable animals build the most biodiverse ecosystems on Earth — and face urgent threats from climate change.
25%
Species supported
<1%
Ocean floor covered
50% since 1950
Reef area lost
Ancient ocean drifters
Jellyfish are among the oldest animals on Earth, predating the dinosaurs by hundreds of millions of years. These simple yet successful creatures drift through every ocean, playing important roles in marine food webs.
500M+
Years on Earth
95%
Body water content
2,000+
Known species
Mammals of the sea
Seals, sea lions, otters, walruses and manatees — marine mammals are air-breathing animals that have returned to the sea. They occupy a unique ecological niche and face significant conservation challenges.
130+
Known species
2,388m
Dive record (elephant seal)
5 orders
Groups
Read Rowan Byrne's expert articles on marine biology, conservation and ocean research.