Lobsters have urine nozzles under their eyes, and pee in each other’s faces to communicate.

When a whale dies and its corpse falls to the bottom of the ocean, entire ecosystems rapidly develop around eating every part of it due to how scarce resources are in the deep ocean. This phenomenon is called a "whale fall" and it's a major source of energy for deep ocean ecosystems.

The ocean has killed more billionaires than the Moon has.

Whales suffocate to death; they don’t drown.

Human breathing is controlled by the autonomic nervous system. We have to hold our breath on purpose to stop ourselves from automatically breathing. This makes us passive breathers. Whales, however, are active breathers. They must choose to inhale which is why they can sleep without sucking in air. When they get too old, sick, or weak to surface, they suffocate.

Bonus fact: whales can’t breathe through their mouths; it goes straight to the stomach. The blowhole is the only respiratory tract.

Bonus bonus: a blue whale’s throat is so small it could choke to death on a grapefruit.

There are lakes in the ocean called brine lakes/pools. Brine is essentially concentrated saltwater; its high salinity means it's denser than water. On rare occasions, brine doesn't mix enough with the existing saltwater around it, sinking to the bottom of the ocean and forming these lakes. The lake itself is usually devoid of life; brine itself is so salty that animals go into toxic shock if exposed for too long. However, the edges usually are full of life, where usually things like mussels and other extremophile organisms thrive.

Side note, subnautica's lost river is based off of this. No big leviathans in real life though, at least none observed yet...

Video for fun: https://youtu.be/ZwuVpNYrKPY

There are entire levels of the ocean where ecosystem is fed on the slow sinking of dying animals.

Greenland sharks are pretty amazing

They can grow up to 24 feet putting them at the same giant scale as great whites and basking sharks, but most are usually closer to 5 meters long

They can live for hundreds of years due to extremely slow metabolism and ambush feeding, some individuals found around 400 years old are as old as the Jamestown colony, Don Quixote, and the discovery of logarithms.

They are opportunistic feeders and have been found with polar bear and reindeer in their digestive systems, and can pull/vacuum in water to catch their primary prey of fish, eels, and other sharks.

Norwegian fjords are freaking deep. When you're on the shore of Sognefjord, you're standing in front of a 1300m deep canyon filled with ocean water.

Sharks are older than trees and the north star.

The Blue Whale is so large, that if you laid one out on a standard NBA basketball court, the game would be postponed.

fun fact: we kill 3 TRILLION animals a year, most of which are sea animals.

While this is funny and all, this isn't really true for a couple of reasons:

• We know a hell of a lot about the oceans, we've studied them for hundreds years. There has been extensive mapping of the seafloor. All of the areas close to land have been thoroughly studied. And where we've spotted interesting stuff, we've investigated for sure.
• We haven't thoroughly explored the moon. Sure we've had nice pictures for a long time. But we've only recently seen the rear side of the moon, as we more or less always see the same side from Earth. Not till recent orbiters we've had a high resolution map of the moon, comparable to maps we have of the oceans.
• Only a dozen or so people have ever been to the moon and the amount of research they did was very low. They also haven't brought back many samples. And the amount we can do from orbit and with rovers is very limited. At this point I would say we know more about Mars than we do about the moon, depending on how to count. The moon isn't that interesting, so we haven't done much with it. It's made of the same stuff as the Earth and without an atmosphere and biosphere, it's kinda dull.
• This is basically impossible to measure. What is knowledge? How is it quantified? We could say it's relative. But since there isn't a way to know how much total knowledge there is available to learn, I'd say that's not possible. What does it mean to "explore"? Do people need to go there? Because a hell of a lot of people have been to the seafloor than to the moon. Hell going to the seafloor is a basic tourist activity these days. I've been to the Maldives and did some crazy dives looking at life on the bottom of the sea.
• People might argue the Moon is basically all the same, so once you've seen one spot you've seen them all. I'd argue that's not true, we've only recently learned the moon's poles are very interesting and we know very little about that. And I'd counter that argument with the fact the same goes for the deep oceans. A whole lot of it is just barren wasteland, an under water desert. We haven't explored because there is nothing to see. We select interesting locations and study them thoroughly, instead of studying a lot of it a little bit and wasting huge amounts of time.
• Another argument often repeated is new species are discovered every day in the ocean. Whilst this is true, we are also destroying a lot of species, so the total number might actually go down instead of up. And a lot of species are variants of already known species. Only expert biologists can differentiate between the species and know what to look for. And I'd argue they don't change the big picture or understanding at all. Still interesting, but not an indication there is so much more to find out there.
• But what about something huge living down there? Like a Kraken or dinosaurs? Well no, we don't have to have studied every square inch to know about big life. Big life is messy, requires a lot of resources and is part of a food chain. You don't need to see the dinosaur if you can see their giant mountain of crap amidst broken trees. There might be some kind of large squid or something down there, but they will probably be extremely similar to other large squid we already know about. So a new species, but not changing the overall picture. If there were any big monsters down there, we would know about them by now.

So this is one of those things that might feel true, but in reality it really isn't.

We are killing the ocean by increasingly acidifying it. This has been known by scientists for decades.

goes to moon

Sea of Tranquility

Nooooooo!

A teaspoon of seawater typically contains about fifty million viruses

https://en.wikipedia.org/wiki/Marine_viruses

Not a fact but a question:

How do whales keep water out of their anuses when they are deep diving?

Whales have been known to dive almost 2 miles deep and at that depth you're looking at almost 300 atmospheres of pressure and a whale's sphincter has to be strong enough to resist that.

Fun Fact: Dolphins fart.

Thalassaphobia is a real thing

Earth's atmosphere is an ocean of gas. The ocean is an atmosphere of liquid. Words are made up.

Global warming has a slower effect on the oceans than in air temperatures, yet we've passed a tipping point where many sea regions are consistently 3C warmer than pre-industrial era, and they are helping air temperatures set records too. Even since 2016, summer tropical North Atlantic ocean has been over 2C warmer than 2016. This region is also called "hurricane alley", and ocean heat has an exponential effect on hurricane strength.