The ocean is home to many parents, but not many "dads". Why? Being a father is hard, and in most cases it's simply easier to scatter huge numbers of offspring into the ocean and hope for the best, or to use those resources to secure mates rather than to protect the young. It's a harsh world in the ocean - but the harshest environments are what form the ocean's best dads.
Let's celebrate Father's Day by taking a look at some of the ocean's most exceptional father figures:
Seahorses (The pregnant dad)
Seahorses and pipefish are perhaps the most famous dads of the sea. Mom does all the work producing healthy, fertile eggs, but when it comes to protecting and incubating the eggs, that's dad's job
Once fertilised, the eggs are stored in a brood pouch that each male has. The male seahorses then protect the growing eggs until the babies are ready to be released into the wild.
Once a female has laid her eggs, her mate will pick them up, using a special extra pair of legs that males have just for this purpose. He will then carry these eggs with him until they hatch - and once they are hatched he'll actually let them crawl all over him and live on his carapace until they are strong enough to no longer need his protection.
Emperor penguins (The stay-at-home-dad)
Antarctica is cold, but hundreds of thousands of emperor penguins call the continent home - and have chosen the middle of Antarctic winter as the ideal time to nest there. Thankfully, they have one of the planet's best dads to make sure their eggs survive the winter.
Both male and female emperor penguins spend summer getting fat on squid and krill in the Southern Ocean. They then trek to massive breeding sites on the Antarctic ice, where each female produces one large egg. These eggs are laid in early winter and passed to the male parent. The females then return to the ocean to recoup the energy it took to produce the egg.
Egg-sitting is then entirely dad's responsibility. The male penguins will spend the next two and a half months protecting their egg on the ice sheet - they never leave, they never eat, they never take a break. Even if the egg hatches, they will keep the chick warm until the sun finally rises at the end of winter and the females return. These dads endure blizzard winds of over 200km/h, unending night, temperatures that drop below -30°C, and they lose half their body weight in the process.
Orcas (Ultimate stepdads)
Orcas have a complex social structure - all orcas stay with their moms for their whole lives, and close-knit families of related mothers form "pods". Male orcas only mate with females from different pods, but they stay with their original pods, so play no role in raising their young.
This doesn't make them lousy dads though - in fact, it is normal for male orcas in a pod to take on some of the responsibility for teaching and caring for their brothers, sisters, nephew and nieces. In other words, male orcas in a matriline are all stepfathers to the calves of all the females in their family.
Cardinalfish (The "don't eat me" dad)
Unlike many fish that rely on external fertilisation, cardinal fish dads don't leave the survival of their offspring to chance. Once eggs have been fertilised, the father will quickly scoop them all up in his mouth for protection.
During this time the dad will actually slowly starve, he won't spit out his young except to occasionally clean them and promote water circulation - but he never sneaks a snack.
Some cardinalfish dads even go a step further and brood their young after they hatch, using their mouths to protect the small fish until they are simply too big to fit!
Happy Father's Day!