Marvels of the Ocean Floor

Learn about the startling features hidden in the deep blue

The depths of the ocean are mysterious and unexplored, but we know it contains incredible things.

Table of Contents

Features of the Ocean Floor

The deep blue ocean covers an incredible 70% of the Earth’s surface. It connects all the landmasses, is an important source of food, and it is still the way most goods are transported all around the world. Despite this, we only know about 20% of the ocean, with the vast majority being unmapped and unexplored.  

The bottom of the ocean is a very difficult place to explore. The depth of the ocean ranges from very shallow near the coast and is mostly at an average of 3,688 meters (12,100 feet). Water is very dense. Anything on the ocean floor experiences an incredible amount of pressure. The deepest humans have ever dived is about 332 meters (1082 feet). Even machines have a lot of trouble dealing with the kind of pressure at the bottom of the ocean.

A modified submarine
A modified submarine designed to withstand pressure and function as an underwater laboratory, Credit: Wikimedia/Jacques Rougerie Architecte

With the exception of shallow, coastal regions and coral reefs, oceans are also very dark places. Light does not reach the bottom of the ocean, which means plants and phytoplankton cannot grow there. The animals that are adapted to live here have some of the most incredible (and bizarre!) features of life on Earth

1. Deep-Sea Gigantism

Light on the ocean floor is a very limited resource. With no plants and phytoplankton surviving without light, nutrients and resources are scarce. Imagine the ocean as layers of a cake. Each layer has specific organisms that are adapted to living in those conditions, and they don’t generally move from one layer to another.  

One theory supporting deep-sea gigantism is that the limited nutrients favor large body sizes. Bigger animals can cover a much larger distance for hunting and foraging. Isopods are crustaceans that live in the deep sea. Massive isopods gorge on food when it is available and can survive without it for up to five years. 

The cold temperatures mean growth is slow, and animals can take their time to reach massive sizes. Colder temperatures also mean cells can grow bigger and live longer, adding to body size.  

Although scientists are still figuring out exactly why deep-sea gigantism is so prevalent, we have observed behemoths such as the giant squid, sea spider, seven-arm octopus, and deep-water stingray. 

A deep- sea giant squid which washed up on a beach, Credit: Wikimedia/NTNU Vitenskapsmuseet

2. The Mariana Trench

The Mariana trench is a crescent-shaped valley in the Pacific Ocean. It is over 2000 kilometers (124 miles) long, and its deepest point is known as Challenger Deep. Challenger Ddeep plummets 10,984 meters (36,037 ft) straight down. At this abyss, there is no sunlight whatsoever, and the temperature hovers just above freezing, between 1-4° ͒°C (34-39°F). This deep trench was formed by the collision of two tectonic plates. Both are the same weight and thickness, so when they push against each other, both are pushed downwards. 

A map of the Mariana trench. The color shows the depth of various points in the trench, Credit: Wikimedia/astrobob

A sequence of expeditions known as Challenger has tried to plumb the depths of the trench. The very first one took place in 1851! Back then, they used a very long rope attached to an anchor to record when the anchor hit the bottom. Now, most of the ocean floor is mapped using the sonar technique. Sound waves travel at a consistent speed in water. When they are sent into the ocean, they hit the floor and are reflected back to the source. Measuring how long the sound waves take to come back can tell you how deep the ocean is, since the speed of sound is consistent. The depth of the Marianas trench was recorded using sSonar in 1951 by Challenger II. 

Humans have actually visited the depths of the Marianas trench in submarines! In 1960, the first manned expedition took place, and humans witnessed the deepest part of the world for the very first time.  

3. The Angler Fish

The angler fish is just the kind of strange, extraterrestrial creature you would expect to find at the bottom of the ocean. Although there are over 200 species of angler fish, the one you have most likely heard of is known as the deep-sea angler fish. A piece of the fish’s spine protrudes outward, hanging over its massive mouth. At the end of it hangs a small, bioluminescent lantern, which produces the only light of the deep sea.  

The light attracts prey, which are lured in by the swaying. Hypnotized, crustaceans and smaller fishes are swallowed whole by the wide maw of the angler fish. Angler fish’s mouths can open to swallow prey that is twice as wide as them!  

The lure also has a secondary function – attracting a mate. Male angler fish find the females by following the light. In some species, the male angler fish fuses with the female. The skin joins, and the male is permanently attached to the female fish until they die. Maybe in the loneliness of the deep ocean, they just don’t want to let go! 

A deep sea angler fish. A small male without the angler is visible attached to the female’s belly, Credit: Wikimedia/Andrew Butko

4. Hydrothermal Vents

Tectonic plates not only form deep trenches, but also underwater volcanoes known as hydrothermal vents. When seawater meets magma, magic happens! The water from hydrothermal vents can reach a temperature of 700°F (372°C). Even cooler than these steam vents are the organisms within them! 

In 1977, scientists discovered microorganisms which could survive without oxygen for the first time! Unlike every other organism on earth which needs oxygen, these marvels can respire sulfur and methane. These conditions are extreme and difficult to imagine. Some researchers even believe the first organisms ever grew near hydrothermal vents, making them the origin of all life on Earth.

Inactive hydrothermal vents, Galapagos Rift
A now-inactive deep sea hydrothermal vent. Gasses come from the tips of the rocks, Credit: Wikimedia/NOAA Photo Library

Every decade, we discover more and more about the ocean. This life-giving habitat is in danger from climate change, overfishing, and plastic pollution. Even in the Mariana trench, plastic has been found. You can eat in-season fish, reduce single-use plastic, and find a way to get involved to protect this incredible place.


Bioluminescent: Light produced by a chemical reaction in a living organism 

Magma: Molten rock found beneath the crust of the earth 

Pressure: The force exerted per unit area 

Tectonic Plate: Pieces of the Earth’s crust which shift and move around 

Flesch Kincaid Grade Level: 7.6 

Flesch KinkaidReading Ease: 66.7 

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  • Yamini Srikanth

    Yamini's (he/they) interests lie in environmental education, science communication and trying to build a better world. When not languishing in front of his laptop, they can be found outside, poking at any insect, bird or plant. They love making science accessible, especially to those who aren't encouraged to pursue it. Yamini hopes that the young women who read Smore love learning from their articles and get just a little bit more excited about science!