That makes sense. I'm going to need to start transferring the 4A torpedoes to 5th edition, aren't I?

This might help.

300 meters typically means it isn't that far from land. Like a hundred km or less.

So this is an Ares site? That means it's probably very well funded and supported, plus it is extraterritorial. Well funded means probably multiple fiber links, plus radio from the surface marker. Extraterritorial means it can have whatever defenses it wants, and if it's studying awakened sea life it will have very effective ones. Obvious would be sonar and lidar detection systems for perimeter, plus video for close in. Being it's researching awakended sea life I'd assume it's warded to hell. Use wireguided torpedoes to deal with serious threats, light RoVs to investigate and deal with minor issues and use green lasers on turrets to deal with serious threats that get in close.

Then there are the spirits summoned or bound by the numerous mages. At least I'd certainly expect that the staff of a underwater base studying awakened sealife would have more then a few mages. And I'd expect that all Ares mages have some fairly decent selection of combat spells plus a few bound spirits in addition to whatever else they might have. For example, one might have a bound spirit that has been to a warded room on the surface inside an Ares security facility where it can yell for help into the PA via a metaplane shortcut.

Critical decision is whether this is a saturation site or an atmospheric pressure site. It's going to be virtually impossible to extract someone from a sat site, as they need about 20 days of decompression. In addition, the players exposed to 300 meter pressure for even a few minutes will need extensive decompression (like a day) before they can be at atmospheric pressure.

So if it's a sat site the players will need an entire support crew along to handle decompression and running the ship that their deco chambers are located on.

So they need a multi-hundred million $ ship or sub, a crew for said ship and a dive medical staff. And this, if successful, will result in seriously annoying Ares. How is this cost effective? How much does this pay?

Some of the health issues could be alleviated with a mage casting Stabilize and Oxygenate on the runners and extractee.

If it's an Ares facility, an alternative suggests itself: wait until they're having a full-on bug hive crisis and sneak in when they're already dancing the Charlie Foxtrot.

Haha. Indeed. Or introducing such a horrible thing into their ecosystem, waiting for said effect to take place, then capitalizing on the chaos.

The thing that seems to pose the most difficult piece of this entire extraction though, is the cost to get down there for the potential reward of doing so. The cost in nuyen is the immediate cost, of course. But the cost in the potential danger of losing one's life in such a hostile environment.. well, this seems like an end run to me. Or at the very least, a prime run.

Back on the materia lside, the hull is likely to be some sort of high performance concrete rather than titanium or other metal - since it's a fixed installation, you don't have to worry about vibrations, pressure changes and weight as you would with a submarine. And it will save a befty bundle in construction costs

That works.

I could swear that there was some mention somewhere in a splatbook of a transparent concrete. If anyone can confirm this for me then in my 6th world there's a variant strong enough for this construction. I invoke rule of cool on this.

Transparent Concrete is mentioned in SR5 pg 363 "Doors, Windows, & Locks" end of the first paragraph.

Que?

How about transparent rebar? I expect you'd need some serious reinforcement at about 30 atmospheres (if my maths are right).

Tangentially, it's threads like this that make me wonder what the karma cost of Dumpshock as a group contact would be.

too much for most people to afford at creation lol

Thanks to the matrix & VR, there probably isn't a lot of need to pull the "Aquanauts" out of the complex for meetings/etc. If the corp frequently moves the people into and out of the facility, then you might as well do the extraction when the target isn't under water, which ruins the fun of the run concept. Moreover, if the facility is capturing and working with deep sea life, or has frequent need to send people into the water, then a saturation facility is more reasonable. It might also be easier to maintain, as the internal pressure would be closer to the external pressure, making access to the water safer. Many real world underwater labs were saturation for these reasons, including oil rig/corp owned setups. Also, I think it's cooler, so it's what I would go with... but that's just me.

To make the extraction possible, I'd probably use magic. Some combination of magical spells can remove the issues with the bends, allowing people to rapidly return to the surface. Using what I could look up on wikipeida, 300 meters is a 20 day decompression at 15 meters per day, but with magic hand-waving and 2070s tech that might be reduced to 20 hours. Sadly this is not the kind of thing that smugglers might be making use of. They might have mini subs for sneaking contraband into ports, but they aren't likely to need to deal with saturation diving issues.

On the Topic Wards
Normal corp facilities often have wards, which can be setup & maintained by a host of wage-mages, the combined magic of which limits the size of the ward. This is actually a lot less likely in a deep water habitat because of the difficult in access to the complex. The ritual participants would need to be physically present in the deep water habitat to cast the ward(s). It's more likely that the wards would be just those setup by the local mages in the complex (if they are studying paranormal animals, they probably have a few mage-scientists). This lack of extra bodies for rituals would likely limit the size of the wards, and thus limit them to key locations in need of protection instead of complex wide wards. It also increases the likelihood that key parts of the facility may be dug into or buried under the sea floor in order to take advantage of the earth being a barrier to astral forms.

Aqua Tech in 5th Edition
There is a mini sub in the 5th edition book, but it only holds 2 people. The Vulkan Electronaut is a lot cheaper and less restricted than I expected, and it's a good starting point for designing other subs the complex might have, or that the players might use to access the complex. There are also the "Proteus Lamprey," which is a 4-person underwater scooter with drone rack.

You could convert the existing 4th edition torpedoes, but for ease of play I'd probably just use 5th edition rocket & missile stats. Underwater propulsion and explosions are very different than air based ones, but that's a lot of added complexity for not much game-play gain, so I wouldn't bother.

4th edition had a variety of underwater projectile weapon options thanks to Arsenal, but 5th edition Core lacks a lot of them (for now). Harpoon guns might be based on crossbow stats. Underwater firearms came in two types: air-fed guns that shoot normal caseless bullets but need to be hooked into an airsupply, and gyrojet exotic weapons that shoot small missile rounds and do +1dv in water, and come with a variety of special (including taser) ammo types. Both can easily be mocked up in 5th edition using the existing weapons and rules and prices from 4th edition.

What's the point of the air-feed ? Even caseless ammo doesn't rely on the surrounding air to oxydize the propellant. About the only use i see would be to drive water out of the barrel when firing.

That makes perfect sense if you know anything about guns. If however you are a SR dev or writer....

Hey, some of us know about firearms and explosives thank-you-very-much!

Have they told you about the operation you need to be promoted to senior writer? It's a frontal something or other.

The Full-Frontal Lobotomy is for Editors. (IMG:style_emoticons/default/nyahnyah.gif) (Or so my Great-Aunt has informed me.).

EDIT: Sorry, sorry. My Great-Aunt was the first person in my family to get published.

Not full frontal vasectomy? (IMG:style_emoticons/default/nyahnyah.gif) (IMG:style_emoticons/default/biggrin.gif)

Isn't that procedure more commonly known as castration?