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Aquatic

Source Galaxy Exploration Manual pg. 52
Aquatic environments have long stirred feelings of horror, wonder, and discovery, for their depths can hold enchanting sights, unfathomable riches, and chilling terrors. On planets with aquatic biomes, adventurers don’t need to travel to new worlds to find themselves in a thrilling new setting.
Even a world with moderate, Earth-like climates might be a maze of thrashing vortexes below the water’s surface, and a world plagued by tempestuous atmospheric storms might have a refuge of calm in the water’s depths. Beneath the surface lie vibrant reefs where magnetic corals arrange themselves in geometric lattices and deep sea trenches cloaked in an icy darkness that seeps into one’s bones. Visitors to an aquatic biome might drift peacefully on a glittering pink lake that swallows them up in its vast expanse or suddenly find themselves whisked away by a waterfall flowing up into the atmosphere.
On worlds with blue skies and clear waters, oceans appear to be blue, but on worlds where the sky is green or the water is mineral-rich, aquatic environments take on hues as varied as the colors on the light spectrum. These environments aren’t limited to just water, either. Explorers might strain to swim through an amber lake as viscous as honey, or they might sweat nervously while navigating a minisub through a series of interconnected, bubbling acid pools. Composition notwithstanding, aquatic terrains are generally more energy intensive to travel through compared to terrestrial environments because water is denser than air. The heightened drag in an aquatic biome means that vehicles must be sleekly constructed for efficiency, and creatures without a swim speed benefit greatly from the aid of mechanical, mounted, or magical means of propulsion.
Civilizations in aquatic biomes might be organized in floating towns, undersea bubble cities, or even amphibious societies that split their time between land and sea. Some worlds might have entire nations built on ships or on the backs of gargantuan sea creatures. Regardless of how civilizations formed in aquatic biomes, they commonly rely on a combination of hunting, foraging, and aquaculture to sustain their populations. Water shapes how these populations grow and evolve, playing a major role in day-to-day life.
Perception works differently underwater than it does on land, requiring some adjustment for first-time visitors. Threat detection might be impacted by turbulent water that limits visibility or by the liquid environment’s amplification and distortion of sound vibrations. Sensory inputs of smell and taste blend together and are challenging to parse for non-aquatic species. This type of environment’s inhabitants require adaptations—whether evolutionary, magical, or technological—to sustain life. While magic and technology make underwater life and exploration possible for non-aquatic species, it isn’t always comfortable. Deep-sea ventures risk water pressure and density that could crush ill-equipped adventurers, and depleted air supplies spell disaster for parties on extended excursions. Drowning is a constant danger, and combat capabilities become limited without equipment designed or modified for aquatic combat.

Aquatic Adventurers

Source Galaxy Exploration Manual pg. 52
Aquatic biomes contain bounties of natural resources and potential scientific breakthroughs that encourage settlement. Adventurers hailing from aquatic biomes might be artisans, ecologists, farmers, researchers, or sailors. They’re typically strong swimmers skilled in Athletics and Acrobatics. While many species that thrive in water have swim speeds, such as brenneri and morlamaws, technology and magic can be used to outfit less aquatically-predisposed species.

Aquatic Worlds

Source Galaxy Exploration Manual pg. 52
Aquatic worlds vary far beyond flat expanses of ocean. In surface or inland aquatic environments, webs of rivers might sprawl over fertile floodplains, or roaring waterfall valleys might lurk behind heavy curtains of mist. The landscape could feature geysers that launch into the air or rivers that drift through the sky. An ocean’s shifting tides might hide trenches with cliffs that plunge into pits of darkness and towering mountain ranges that rise from the seabed to create island chains above the surface. Currents replace terrestrial rivers, and aquatic forests of kelp reach toward the light of the surface. The sun warms the shallows, and aquatic life displays vibrant colors, illuminated by rays of light that pierce the sea. As one descends toward the core of an aquatic planet, the darkness is alleviated only by the lustrous glow of undersea cities or the gleam of magical or bioluminescent species. Looking up from the watery depths, the shadowy underbellies of aquatic life drift by, the danger they present unknown. Deeper still, temperatures drop and water density rises. The crushing pressure might make mobility challenging, and temperatures can verge on extreme, unlivable lows; signs of life are few and far between. The species that thrive in these extreme ecosystems have terrifying advantages over unwary travelers, such as those lying in wait with dancing lights that lure prey into their gaping maws.
Aquatic civilizations, like the ebb and flow of the tide, constantly change. Some develop in caves, are woven into kelp forests, or spring up from the calcified remains of once-fearsome leviathans. Undersea bubble cities designed with the comfort and survivability of non-aquatic species in mind require astronomical resources. Some settlements are constructed out of necessity as avian and terrestrial species flee catastrophic weather on their planet’s surface, while others start out as small research outposts and evolve into cities of science. On the surface, cities might float or be constructed on stilts anchored in lake beds, with floating bridges connecting different districts and buildings. Deep-sea cities might also depend on current-sourced hydroelectric power or volcanic heat, while those near the surface might harness energy from waves or waterfalls to power daily life.

Aquatic Rules And References

Source Galaxy Exploration Manual pg. 53
Starfinder already has many rules to aid in aquatic adventures. Information on swimming appears on page 137 of the Starfinder Core Rulebook, and details on swim speeds appear on page 259. While several species can breathe underwater, those that don’t will find the mechanics of suffocation, drowning, and aquatic combat on pages 404–405 particularly useful. The Aquatic Terrain section in the Core Rulebook (page 396) describes terrain that players might encounter, including rules for adventuring in deep water and extreme deep water, as well as limitations on underwater perception. The Falling into Water section (page 401) details fall damage and diving mechanics, while the Heat Dangers section (pages 402–403) describes damage taken by exposure to boiling water. Not all creatures are adapted for aquatic adventures, and those without natural swim speeds can make use of cybernetics, such as gill sheaths (Core Rulebook 211). Standard starships aren’t designed for use in water, so vehicles ideal for aquatic travel, like minisubs and hoverpods (Core Rulebook 228–229), can also prove useful.
Use your imagination to craft your own vibrant aquatic worlds, or take inspiration from the sarcesian underwater dome colonies on Nisis (Pact Worlds 85), the dark waters of The River Between that wind through the Diaspora (Pact Worlds 86), and the icy depths of Dahak’s Claw on Triaxus (Pact Worlds 104). The island-dotted Vesk-2 (Near Space 26–31) and the pink Basin Sea of Vesk-3 (Near Space 36) provide further examples of aquatic settings.

Aquatic Toolbox

Source Galaxy Exploration Manual pg. 54
See Biome Subsections on page 46 for advice on how to use the following tables.

Aquatic Inhabitants

D%	Sapient	Threat
1–4	Bone trooper	Anacite
5–8	Brenneri	Atlapak
9–12	Calecor	Bloodbrother
13–16	Cephalume	Cargo creep
17–20	Cerebric fungus	Cloud ray
21–24	Corpsefolk	Diaspora wyrm
25–28	Dragon, black	Dinosaur, plesiosaur
29–32	Dragon, bronze	Elemental, water
33–36	Genie, marid	Elmeshra
37–40	Ghoran	Giant, storm
41–44	Ghoul, lacedon	Glass serpent
45–48	Ijtikri	Haan
49–52	Kalo	Hashukayak
53–56	Mephit, water	Herd animal, aquatic
57–60	Morlamaw	Jakkerant
61–64	Oracle of Oras	Jubsnuth, aquatic
65–68	Osharu	Kami
69–72	Planar scion, undine	Ksarik
73–76	Scyphozoan	Kyokor
77–80	Spathinae	Mephit, water
81–84	Stellifera	Muotta
85–88	Telia	Murzzilat
89–92	Vilderaro	Osifern
93–96	Woioko	Predator, aquatic
97–100	Wrikreechee	Wysp, water

Aquatic Adventure Hooks

D20	Adventure Hook
1	A large and biodiverse coral reef is inexplicably dying—though the recent arrival of a controversial pharmaceutical company just up-current from the reef draws the suspicions of the planet’s inhabitants, who look to outsiders to investigate.
2	A deep-sea fishing vessel recently discovered the underwater wreckage of a massive, interplanetary research starship. The starship in question disappeared without a trace years ago amidst controversy over the ethics of its research.
3	Unusual geothermal activity has been reported near an underwater settlement. Scalding water spouts from small holes with unnaturally even spacing, stretching for miles and appearing to form a seam on the ocean floor. Are they relics of a past civilization, an incursion from deep below the world’s crust, or something even stranger?
4	A planet’s kelp forests are a hot spot for tourists, but rangers charged with protecting the natural resource have become perplexed by a wave of recent reports of nonaquatic creatures attacking visitors among the forest’s deceptive, twisting strands of kelp.
5	Each year, a small settlement hosts a months-long festival of lights during the planet’s bioluminescent algal bloom. This year, during the peak of the festival, all the algae instead began to exude an ominous, purple-black light, pulsing together to an unheard rhythm.
6	The PCs win a stay at a deep-sea luxury hotel. Their suite is a large pod with 360-degree views of the artificially lit ocean floor. Their first night there, the lights flicker and go out, immediately followed by the first of many distant screams.
7	While conducting seismic imaging in search of natural resource deposits, scientists are shocked to discover two massive, inverted pyramids buried beneath the ocean floor.
8	A rare disease leaves many of an archipelago nation’s children in critical condition. The only known cure is the nectar of a flower that blooms only in the deepest chambers of aquatic caves guarded by territorial sea-born predators.
9	Amidst a prolonged famine, officials introduce a new, edible species of sea slug genetically modified to adapt to unfavorable conditions. The slugs turn out to be a little too adaptable, and they begin feasting on the town’s inhabitants.
10	Magical, spherical pockets of oxygen-rich atmosphere have begun springing up randomly, with devastating consequences for the aquatic flora, fauna, and sapient creatures. Did this phenomenon result from an incursion of the Elemental Plane of Air or perhaps a failed magical or technological experiment?
11	A large, drifting city suddenly pulls away from its projected trajectory by a mysterious new current. Reports from nearby cities indicate they’re all spiraling toward one central location of concentrated magical energy.
12	A small research station located on the perimeter of Reaper’s Basin, a deep-sea methane lake, has sent out a distress signal. At the station, the researchers have vanished with all that remains being their uniforms neatly folded on chairs around a table set with still-warm food.
13	The massive domes protecting a sprawling city on the sea floor have inexplicably begun to crack, sending mass panic through the air-breathing populace.
14	A film crew working on an action vid blockbuster is woefully underprepared for shooting deep underwater. To make matters worse, what equipment they do have is being methodically sabotaged, putting dozens of lives at risk.
15	Locals whisper of an iridescent ghost ship that appears on moonless nights over the wreckage of a sunken merchant vessel. When it appears, screams issue from the vessel before it rends in two and sinks beneath the waves.
16	Communication with an underwater city has been cut off, and the only access to the trapped population is a network of massive elevators and platforms initially built to transport equipment for the city’s construction.
17	An island known for its picturesque, sandy beaches has become a stinking isle of rotting fish and marine creatures. It seems something in the water has caused the creatures to beach themselves out of desperation.
18	For the past month, seaweed-draped skeletons have marched from the ocean each night to terrorize a coastal town. Rumors connect the attacks to a necromancer who was exiled from the town years ago.
19	A submarine cruise liner has abruptly ceased communication with the surface world. Analysis of its final messages seems to indicate that its crew and guests have become zealous initiates of a dangerous cult.
20	A gargantuan deep-sea creature has absconded with an entire undersea research station that contains invaluable data and equipment. Retrieving these valuables will require navigating the creature’s cavernous lair filled with parasitic threats as well as finding a way to safely extricate the building itself or the resources within from the belly of the beast.

Archives of Nethys