WALKING WITH THE OCEAN'S INHABITANTS
- Friendly Fins
- Dec 9, 2024
- 5 min read
Updated: Mar 8
How do marine animals move?
We will have experienced first-hand that moving in water is in some ways much easier: we float and feel less of the weight of our body than on dry land, but in others it is more complicated! Our usual movements such as running and walking are almost impossible!
However, what is it like for marine animals to move in water?
Sea dwellers are by far the group that has had the greatest differentiation throughout history, even in their way of moving!
But the oceans's inhabitants are not the only ones who enjoy this environment… We will discover how different animals have “learned to swim”!
Let's get started!!!
Speaking of fish
The fins
Fins are the part of the body that determines, more than anything else, the movement of the fish. But think about it… the movement of the body must be “suitable” for the environment in which it lives… The classic phrase “like an elephant in a china shop!”, well the china shop is certainly not the environment for an elephant! Let’s imagine in the sea…
“It wouldn’t be very comfortable to have a great white shark prowling around the crevices of a coral reef or a seahorse in the open sea!”“It wouldn’t be very comfortable to have a great white shark prowling around the crevices of a coral reef or a seahorse in the open sea!”
If we observe the coral reef fish we immediately notice that each family has its own way of swimming thanks to the specific shape of the body and fins, in this way they have been able to carve out their own "niche". Let's see some examples...
Butterflyfish are beautifully streamlined and laterally compressed, with small fins that allow for quick, precise swimming so they can easily pass through the labyrinth of corals.
Clownfish and domino fish are small, with large fan-like fins, ideal for moving harmoniously inside their anemone. They have found the perfect shape to live in that particular habitat!
The tail
“Think about how different a shark’s tail is from a seahorse’s! And yet we are still fish!”
The tail is a powerful propulsion tool, especially for “sprinters” such as large pelagic animals: tuna, sharks, swordfish. We recognize them immediately because they have a sickle-shaped tail.
Their movement is undulatory from right to left, an important distinguishing feature to avoid confusing them with cetaceans; in fact, their tail moves from bottom to top and not lateral.
“This little trick can come in handy when you see a fin coming to the surface! Based on the movement it makes, you can understand if you are looking at a dolphin or a shark! I bet you already remember it, huh!”
The little tail of the seahorse is more of a “fixing” organ than a propulsion organ, in the sense that it is very useful for holding on to coral or anything the seahorse finds underwater that can be useful as a “perch”!
The body
When does the whole body move when swimming?
This is the case of moray eels, conger eels, sea snakes. The snake-like movement of these animals makes them very skilled at sneaking into crevices to hide but also very fast at hunting. This particular swimming style makes them closely linked to the seabed or close to it, where they can easily find prey but also a safe hiding place.
“You will never find us in the open sea!”
What about eagle rays and stingrays? Their pectoral fins have expanded so much that they have become one with their body, creating their typical disc-shaped shape. They move through undulations and are perfectly adapted to life on the seabed; they would not be suited to swimming in the open sea like their cousins, manta rays, mobulas and eagle rays.
“We like to stay close to the bottom so we can blend in and wait for our snack, why struggle in the open sea when dinner is served comfortably on the sand?”
Even manta rays and eagle rays have modified their two pectoral fins by lengthening them, creating a sort of “wings”; in fact, they move gracefully in the water column like real birds, performing the so-called underwater flight.
Not only fish as inhabitants…
The tentacles
Not just fins and tails! Some animals like octopuses use their long tentacles to move along the bottom or swim for short distances, they are also very efficient propulsion organs: just a "blow" of the tentacles and our friend the octopus has already moved away from us. The same thing for cuttlefish, octopuses and squid.
“If you happen to find a squid underwater wandering around the coral reef, you will notice that it will distance itself from you by swimming backwards precisely because of the propulsion produced by the tentacles that are found on the snout around the mouth!”
Clumsy on the outside but dancer on the inside
Let's get closer to mammals... When we say "to be as clumsy as a seal", it's not entirely accurate!
Animals such as pinnipeds including sea lions and seals, at first glance, out of the water might seem a bit funny, but underwater they transform into graceful dancers and very skilled swimmers.
“We sea lions love to wander around the Kelp, do you know what it is? They are very tall algae that create real underwater forests. Thanks to our strong fins, hydrodynamic and sinuous body, we can make the funniest photographic poses, like this one!”
Wings and legs transformed into fins
Not only some mammals have decided to live their life or part of it in the sea like cetaceans and pinnipeds but also some reptiles and birds!
Think of sea turtles that have modified their legs into very efficient flippers suitable for underwater flight and no longer for moving on dry land:
“We are able to swim very fast thanks to our front “fins” that give us a strong push. This adaptation has allowed us to colonize very different environments such as coral reefs and the open sea!”
Even some birds have preferred to adapt to living in the sea rather than on land, even though they are still tied to it for nesting.
An example are the gannet bird, fascinating birds that mostly colonize the high cliffs overlooking the sea in temperate zones, even in Italy! There are many species of boobies but the most famous are the white ones with the eye that seems "made up" as in the photo below and those with blue webbed feet! These animals are able to hunt fish by diving into the water at great speed (100km/h) and "literally swimming" with their feet!
“Better not to get caught in our trajectory!”
Other birds, easier to meet are the cormorants, they are black and often stay near the sea with their wings open to dry their feathers after the dive of the meal! They too are very skilled swimmers thanks to their strong webbed feet that they use as flippers!
The penguin: its wings are real fins with which it can swim in depth and hunt fish very skillfully. Over time it has developed its swimming skills so well that it is no longer able to fly like other birds!
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