kerbiloid

Afaik, they are "alternative humans".

Of course, life can exist on underwater mountains, but this meets two disadvantages: 1. Low total area of their peaks near the surface. 2. Underwater mountatins are mostly mid-ocean ridges, where the young oceanic crust rises from the mantle. So, these areas are nearly as good for continuous living, as giant stars are: live fast, die young. So, if imagine an underwater low-depth equivalent of the Easter Island, which became populated a thousand years ago or so with species from another place - why not.

6. Those little LEDs or lamps inside the spacesuit helmets. I hate them. They make a serious, clever and brave human look like a moron and a target at once. The only exception: Prometeus. In this movie it's OK: they are indeed morons. And targets. From whose point of view do you count? Indogenes or Castithans? Here are Stahma Tarr with her spouse (they rule this movie), one ET girl adopted by a brutal mass murderer (the main hero), and four humans (well, more or less after all).

As the planet can contain enough thick atmosphere to prevent the oceans dissipation, we can be sure that its gravity is at least Earth-like. So, every + 10 m of water depth = + 1 bar of pressure. I'm afraid that it's much easier to have a spaceship for 0.3..1 bar as the humans do, than a spaceship for 100 bars which is absolutely required for the creature living at 1 km below water. Due to the physicals laws, 100 times greater the pressure → 100 times must be thicker the ship envelope. So, instead of, say, 3 mm of steel, they would need ~30 cm. P.S. Probably, the waterworld astronauts must be not a natural creatures, but a forgotten artificial life. And the same about their planet. Then you can make assumptions which weaken.the requirements. P.P.S. Maybe Cameron's 1989 movie "The Abyss" is something similar what the topicstarter wants. This guy's suit is filled by a fluorine-based special liquid which helps him to stay alive under great pressures. He is literally breathing with liquid in his lungs. See also: Liquid Breathing.

If several hightowers are bound into a single pattern with horizontal struts, the stresses can be distributed through all the city and supressed. P.S. Offtopic: Yesterday I've placed a Kerbin-Side's "Arcology" object on Gilly. This looks amazing...

No HQ images?.. http://buran.ru/

The sole and ultimate condition of an interstellar 'spedition: geographers decide. Such enterprise is so expensive and dangerous and has too low chances to undertake it at random, that you shouldn't "think", you must "know", what exactly you're going to get. No "maybes" or "suddenlys" are allowed, because such expedition will technically and economically cost more that all previous flights together. So, a target for this mission should be not "look at star, maybe find some planets", but "we need a close study of the Thayaphaeawoed continent on the Alofmetbin planet, due to the enormous presence of thorium lines in its spectral pattern". I.e. while the exoplanets are the astronomers' subject, rather than geographers' one - all you need is more telescopes to sharpen their picture. Once you have an exoplanetary globe rather than tellurion, then the journey is a deal.

Side A bursts 40 Mt in the ionosphere. Space war is over. GPS too.

A pack of orbital beyond-Neptune telescopes with ~100 AU triangulation base, synchronized with each other. After getting high-resolution detailed description of every star system, select the one to be investigated. - In any case really interstellar propulsion system won't be available earlier. - Several decades later the humanity may drastically change its understanding of "perspectiveness". For example, closed-loop artificial biomes may make unimportant "habitable zone" idea, while closed-loop resource recycling may drop down any interest in extra-terrestrial mining. P.S. But as we must build Babylon-5 near e Eri, the sooner we start - the sooner we finish,

A repaired old craft = +1 old damaged craft. -1 unborn new craft. Satellite and rocket manufacturers will cut production and fire personnel if such refurbishing takes place. Hardly associates with a progress in the space. Also if all satellites were being repaired, you were still using pagers instead of smartphones. Mother teaches daughter: - Do you see our daddy? Everything in our home is always being repaired by his own hands. Furniture? By his own. Electricity? By his own. Bathroom? Also by his own. Even old toasters, kettles and cooking pots. Really golden hands! So, daughter, if you will ever meet somebody like him... ...Run away as fast as you can, or there will never be at least one new thing in your home!

Experiment with dogs http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660005052.pdf http://www.geoffreylandis.com/vacuum.html

Not exactly about water species, but on a similar theme: Robert Sheckley, "Hands Off"

A paranoic ET from Niven's novels. Hi-Tech, making opaque spaceships, with his/her brain between necks and mouths instead of hands. Brain is in the head because it appears from the biggest cluster of neurons, and so the .main sense organs do. Large eyes are just bulges on the brain, So, when the organ of decisions is close to the organs of sense, you get the fastest reaction. As all creatures are initially worm-alike, because there is a compact creature itself (an input side from one end, an output side from the opposite one) - and numerous primitive additional segments in between. So, if the "input end" becomes enough large and separated, the biggest ganglion is placed somewhere there. Arthropods have their brain not in the "head", but in the second body segment just because their "head" is in fact just a "face", The eyes of vertebrates are just the most evolutionarily advanced eyes. Cluster eyes are just an intermediate primitive form between the primitive eyes of the lowest creatures (and also too poor for a space pilot) and the complex eyes of insects and vertebrata. Faceted complex eye of an insect is just a primitive futureless solution with a very limited distance of view, Enough for a tiny creature with exoskeleton, but almost blind at the human-sized scales and distances. Our complex eyes is, like a faceted one, a reticulum of sensible cells, but united in a single and complex optical system with a great scalability, adjustment speed and with weak evolutionary limitations.

And they will live in coral houses, but they can't eat coral. Hydrogen also requires oxygen to be used instead of gasoline. Also it needs a steel chamber to be burnt/exploded inside. unsquidded

People achieve agriculture because they live under the Sun, not under the water. Underwater plants do not give two-three harvests per year, while the plankton doesn't need metal instruments to be cultivated. Axe or hammer also don't give him any gain because the drag force of the water will slow it down. Underwater you can ony bit with a pike. So, as humans used stones all their hundreds-of-thousand-years history except last 8000 years, the squid also will be happy enough with the shells. Light in the sky is not too important for the squid because of low productivity of the bottom-grown pplants. Squid will be either carnivorous (so, no clear purpose for light), or omnivorous (eating also a plankton). Also: humans return to water to gather more food, and what can find a squid in the air?

Probably, a quasar pair of jets would be visible from far distance.

Btw "Alien" is a 1979 movie, when there were green text displays and typewriter as a secondary (sometimes primary) terminal. They just combined green display with a typewriter-like sound.

Such picture would be extremely blurry. Btw: if humans could do so, whether would they bother with precise glasses and mechanical system of the telescopes?

5. A command "Fire!" given to the archers.

Yes, we are. About electrolysis and electrochemistry. Do not mix two different cases: whether somebody can construct underwater technological species, and whether can it appear evolutionarily.

Well, let's take any human spaceship and just fill it with water. Let it circulate enough fast, so all wastes are filtered out and the oxygen is regenerated while a small part of this water is outside the cabin, while the most part fills the cabin. As the inner space of a pressurized cabin is ~ 5 m3, this means they would launch, say 8 t of water and additional pumps. This would require Saturn to launch Gemini, while they poorly can build at least V-2.

On a Carbon planet orbiting around a white dwarf the ocean creatures maybe have the best chances to rise a civilization. In a methanol ocean, under carbon oxides atmosphere, near a hydrocarbons covering the rocky crust, As the only way avalable for them is chemistry, then with such background they would easily create enormous amount of chemical composites, solvents, glues and other. So, atmospheric balloons, large organic structures, maybe even some rails to sky, But yet not space flights, only high atmospherical. Looks that the main way for oceanic creatures to can into space: to await a large asteroid which hits the basin. They don't need water exhange. They need solved oxygen exchange.

It's enough hard to develop metallurgy when the molten iron contacts with water which cools it down. An iron metallurgy is unavailable for them because they just couldn't build a smelter with dry coke and oxygen-rich air, People did that only in XVIII centurt. Copper, lead - maybe. Also there is water. Axes, hammers and arrows are useless due to the drag force. The only purpose of metal instruments: pins and pikes. But they have enough bones and poisons foir it.

And instead of several kilograms of air they need to permanently pump several dozens tonnes of water.

A human-sized animal requires 1 kg of Oxygen per day. This means a 5 kg pressurized cylinder. Difference between water "poor" and "rich" with oxygen is ~1-2% of oxygen. So, you would get a huge basin to replace water in a small tank. Or - a 5 kg cylinder. Some necessary conditions to get a civilized lifeform: 1. Some actuators like "arms+hands". Absolutely useless for fish-shaped animal. Absolutely great for bottom dwellers. 2. Ability to collect items, store a food. Unavailable for fishes. Lifestyle of bottom dwellers. 3. Ability to use and transform the surrounding media for attack and defence. Poorly available for fishes. Lifestyle of bottom dwellers. 4. Ability to consume different types of food to prevent mass extictions. More or less available for fishes. Lifestyle of bottom dwellers. So, the only oceanic lifeform able to achieve at least a stone age level is either Kraken, or (ta-dam!) Mantis Shrimp.