Locations on the Briny Seas

1. On/In the shell of a: (roll a d4) 1 - gigantic crab, 2 - huge turtle, 3 - mega snail, 4 - humongous nautilus
2. In an underwater air bubble held up by: (roll a d4) 1 - an underseas cave, 2 - ancient and powerful magics, 3 - the machinery of some long extinct race, 4 - the will of the old gods of the seas,
3. A sunken ship; it once carried: (roll a d10) 1 - vast treasures, 2 - explorers from distant shores,         3 - very important people, 4 - a secret, 5 - slaves, 6 - something terribly dangerous, 7 - a message,   8 - a hostage, 9 - a home, 10 - soldiers and weapons
4. A building held down by kelp rope; it is home to: (roll a d6) 1 - a sea hag, 2 - a giant eel, 3 - fish men, 4 - a lobster prince, 5 - a reclusive wizard, 6 - an aging sea god
5. An old lighthouse; it: (roll a d6) 1 - was purposefully destroyed, 2 - leads ships astray, 3 - is haunted by sea spirits, 4 - it is the only ‘safe’ place for miles and miles, 5 - marks a deep and half-drowned dungeon, 6 - leads somewhere away from the waves
6. A lonely island, that is: (roll a d10) 1 - little more than jagged rocks, 2 - a jungle ‘paradise’, 3 - a series of tall peaks, strung with rope bearing a hanging city, 4 - alive!, 5 - the home of a trapped creature, 6 - the site of a wizard’s tower, 7 - only a fraction of a vast and dying whale, 8 - the only source of a rare commodity, 9 - all that is left of a shattered land, 10 - what nurtures an alien ecology
7. A mighty coral reef, it is: (roll a d8) 1 - the flesh of a sea god, 2 - poisoned and dying, 3 - the home of mighty predators, 4 - a key ingredient in many potions, 5 - a mermaid palace, 6 - the prison of an elder god, 7 - traced in the shape of an enormous sigil, 8 - tended to by coral-giants  
8. An underwater volcano, it was: (roll a d4) 1 - the tomb of a slain fire-deity, 2 - worshipped and lived upon by fish-folk, 3 - forge of the weapons of the underwater empire 4 - a road to hell itself
9. A raging Whirlpool that: (roll a d4) 1 - houses an opulent palace at its uttermost bottom, 2 - is a portal to a far, far off place, 3 - is the mouth of titanic sea-beast, 4 - is sentient; it hunts ships gleefully
10. A deep, deep sea-trench, it is: (roll a d10) 1 - the realm of the old, old gods, 2 - where the first men took shape in the primordial floes and whorls, 3 - where a god wounded the very world, 4 - the grave of a great city, swallowed by the sea, 5 - riddled with tunnels, which the home of a titanic octopus, 6 - a realm of preternatural darkness, 7 - a city to those who have never tasted the light, 8 - the resting place of a fallen star, 9 - a flooded, sunken underworld, 10 - a road to the empty and hanging roots of the world
11. A sunken city, it: (roll a d8) 1 - was cast down in its prime, 2 - is now inhabited only by ghosts, 3 - bustles with all the peoples of the sea, 4 - is ladened with slowly corroding treasure, 5 - is ruled by he who declares himself ‘king of all the sea’, 6 - teeters on the precipice of some vast abyss, 7 - is the hunting range of cackling sea-demons, 8 - is a monument to wrath of a god
12. Pillars of rock, billowing inky smoke; they are: (roll a d6) 1 - the dwelling of a mysterious sea-oracle, 2 - home to the shadows of the departed, 3 - the gills of some titanic, continent sized creature,          4 - shrouding something secret, 5 - the vents of some chthonic industry, 6 - home to some ancient beast, the last of its kind.

Modifications for the above results:

1 - only appears/is accessible at certain times,

2 - is only here for a little while longer,

3 - is fiercely guarded,

4 - it wanders the sea-bed,

5 - beloved by sea-spirits,

6 - appears to have been created in some unnatural way,

7 - is the resting place of things lost to the currents,

8 - is sentient, and powerful.

9 - is buried beneath underwater sand-dunes,

10 - is the temporary home of a wandering sea-god,

11 - is a pirate hideout,

12 - is well known, and a way-mark for many sailors.