[SpruferMLB]

It just crossed my mind today what would happen if you were to say, dump a Space Marine in the ocean? I was also wondering if there were any chapters specifically equipped for aquatic combat, similar the specializations of other chapters?

[Koval]

The Space Wolves had a thing in their Codex where they fought Tau underwater in Land Raiders, but that's probably not quite what you're after.

I imagine a Space Marine in power armour would just sink and have to rely on his rebreather to stay alive. Go too far underwater and the pressure would crush him inside his armour. Terminators would arguably have a better shot of survival.

[greenstuff_gav]

im not sure about pressure, but a SMs 3rd lung can process the oxygen from the water.. plus marines can operate for a limited time in vacuum so i suspect deep water wouldnt bother them too much :-)

i know in Xenos Eisenhorn comments on a marine not adjusting his aim for odd gravity so dunno how the water will affect their aim either...

[Koval]

Oh, I agree that the actual being-underwater part wouldn't be too much of a problem (for a while, at least; I don't recall the multi-lung actually giving a Space Marine a working set of gills, so he still has to worry about a load of water inside him), but when you end up trying to repeat Twenty Thousand Leagues Under The Sea, suddenly we have to start worrying

[Necris]

There is a space marine chapter that has a fortress monetary on the ocean bed of an aquatic world, they specialised in aquatic combat, I can't remember the name of the dammed chapter though I think it is in one of the eisenhorn books though

Found one

http://warhammer40kfanon.wikia.com/wiki/Azura_Tridents

[MarcoSkoll]

I'd point out that is the fanon wiki. Not without its uses (some members contribute some good ideas or artwork), but certainly to be taken with a very big pinch of salt.

~~~~~

It's possible that Space Marine chapters do specialise in underwater combat, but I'd say it'd be rare. Humans don't survive very well underwater, and water inhabiting creatures don't survive very well on land, so there's not often going to be a conflict of interest.

If there was a full-on specialisation, I'd expect modified bolt shells - possibly similiar to the Shkval torpedo (to combat the very high underwater drag); maybe underwater thrust packs (visually somewhat like jump packs) and armour with fins (although probably quite small) to help underwater manoeuvring, but definitely considerably increased air reserves.

However, I think the role might get assigned to one of the chapters with extra "space" in their Space Marine. In many ways, the environments are similar (partial counteraction of gravity and lack of a breathable atmosphere),with the biggest difference being the different drag forces.

[Ynek]

...with the biggest difference being the different drag forces.

Also the pressure differential.

In space, the pressure is near zero. At the bottom of the ocean on a terrestrial planet, it can get up to a few hundred times atmospheric pressure. Whilst space marines can survive in low pressure environments for a time without significant side effects, I don't think the same could easily be said of a high pressure environment. It's like the difference between a bathysphere and a space shuttle.

Although, on a horizontally related topic, I often found it odd that Space Marines are called Space "Marines" when they don't really have any connection to the sea. I know that it's meant to play on their relationship to the marines in the modern infantry, but the marines are called the "marines" due to their connection to the Navy, and therefore, the sea. It just strikes me as odd that the Space Marines hold the same name.

[MarcoSkoll]

Also the pressure differential.

A fair point, but the earlier limitation comes into play - at the point the pressure differential becomes significantly large, how many things are there actually going to be down there posing a threat to humans that a specialist chapter is needed to fight them?

I often found it odd that Space Marines are called Space "Marines" when they don't really have any connection to the sea.

See this trope.
It's usual for space to be portrayed with naval elements. Just look at all the different classes of Imperial space craft - or space ship, if you prefer - destroyers, frigates, cruisers, battleships... and then we have the Imperial navy, fleets, commodores, admirals, boatswains, midshipmen, ensigns, etc, etc, etc, etc, etc and so on and so forth.

[Shroud]

From my understanding the Multi-Lung is able to extract oxygen from low oxygen or poisoned atmospheres as well as water. It is also mentioned in HH False Gods that it is virtually impossible to drown a Space Marine. This coupled with their Power Armour would mean that the only thing that would really bother a Space Marine about Oceanic combat would be the Pressure.

plus marines can operate for a limited time in vacuum

   
Marines cant operate in a vacuum without their armour, they can survive thanks to a combination of the Sus-an Membrane and Mucranoid.

[Koval]

plus marines can operate for a limited time in vacuum

   
Marines cant operate in a vacuum without their armour, they can survive thanks to a combination of the Sus-an Membrane and Mucranoid.

Gav didn't actually mention armour, so you're the first person in this thread to bring up Space Marines fighting outside of their armour.

[Dolnikan]

If I recall it correctly the Space Marines can use their third lung to filter gasses, so they can breath everywhere where you can find oxigen in the air. But I never saw any mention of them having anything approaching gills, so they will have to keep their armour on underwater. Otherwise I think that when they fight underwater they will indeed use modified bolt shells, and will otherwise do things the same way as usual. Their heavy armour would ensure that they would sink to the bottom so they will have to walk, swimming will be quite hard to do due to the weight. Normal movement will also be hampered because the water is harder to walk through than the normal air.