Sea Islands and Locations for Dungeons and Dragons 5e

"A flat island, mostly covered at high tide. Low tide reveals hundreds of entrances to an extensive cave system"

Tables for Wild, Civilised and Unusual Islands and locations. Result is from Unusual Islands.

Locations for unusual terrain - jungle | road | ruins | sea | shadowfell

[Photo by Caitlyn Wilson Webb on Unsplash]

Sea Encounter Locations

While the sea is defined by a large amount of water, it can be broken up by islands, reefs and sea going vessels. Encounters might take place on a volcanic isle, a sinking ship, a large sandbank or a statue jutting from the sea.

There is a 5e random encounter generator at ChaosGen. And a separate tool for encounter locations

There is also a pdf of these and more tables at the DM's Guild as Sea Encounters.

Sea Wild Locations

d8+d12	Sea Wild Locations
2	An area of permanent mists (it leads to a sea thousands of miles away)
3	A floating iceberg (there is debris floating in the water)
4	Churning waters with a maelstrom in it's center (it is a portal to a plane of water)
5	A verdant island which is actually hallucinatory terrain over jagged rocks (there is distant thunder)
6	A long sandbank with the skeleton of a large dragon (there is a whirlwind approaching)
7	An island with several palm trees (a flock of gulls circles nearby)
8	Reefs that are hard to spot (there is a floating sign warning of pirates)
9	An island with lots of greenery and a sheltered cove with blue cliffs (there is a floating sign warning of sea monsters)
10	A mass of stinking, rotting seaweed (there is a rowing boat floating nearby)
11	A rocky island with several trees and flocks of seabirds (there is something large in the water)
12	A pair of jagged rocks (there is heavy mist)
13	A rocky island home to thousands of crabs (one of the crabs is a druid)
14	A sandy beach covered in seashells (there is a chilly wind from the northwest)
15	An island of shiny sharp black stone (there is a floating corpse)
16	Shoals hidden by a hallucinatory terrain
17	An island covered in seaweed (a patch of seaweed is intelligent)
18	An area of roiling fog (it is a portal a plane of air)
19	A circular island with a lake at its center (it is associated with a mysterious priest)
20	A permanent storm which travels the seas (it is the avatar of a sea deity)

Sea Civilised Locations

1d8+1d12	Sea Civilised Locations
2	Three rocks carved with images of a sea deity (is in the area of a forbiddance spell)
3	A giant construct of metal, kept afloat by clockwork (there is a maelstrom)
4	A large rock with several nests made from debris of shipwrecks (it is home to harpies who are sometimes friendly, sometimes hostile)
5	An island of crystal that enhances sounds. There are carvings of merfolk playing instruments (there is a merchant ship in sight)
6	A hamlet on the back of a giant turtle (it is populated by lizardfolk)
7	A small island containing crude wooden structures (it has castaways - roll on Ship Crew lvl 1-4 or 5-10)
8	A floating structure with several wooden platforms. At its center is a shrine to a deity of trade (there is a sea elf watching)
9	An abandoned floating prison (there is a brisk breeze from the northeast)
10	An island of windswept dunes dotted with lifelike stone statues (it is overcast and there is light rain)
11	A recent shipwreck on a set of jagged rocks (it is associated with a mysterious spirit)
12	A green island home to a herd of giant goats (a pair of cyclops look after them)
13	A barnacle-covered shipwreck surrounded by kelp (it attracts many octopi)
14	A barren island with a stone circle (associated with a dangerous shapechanger)
15	A floating stone temple to a deity of the sea (a winged creature is circling high overhead)
16	A platform of dwarven (or gnomish) design with an abandoned hamlet. It is anchored to the seabed (nearby is a small island)
17	A bronze statue rising up out of the sea (many dead fish are floating here)
18	A giant beanstalk rising up from a forested island (there is a planar portal at the top)
19	A spire of bronze that rises from the sea floor. It has a staircase spiraling around the outside (the area is unaffected by storms)
20	A large wooden cube with steps carved into one side (it is disguised by a mirage arcana)

Unusual Islands

1d8+1d12	Unusual Islands
2	An floating ice castle with cold wintry weather in a few miles around it. An intelligent frost weapon is buried here (it is associated with a storm giant scholar)
3	A wooded island blessed by a powerful fey. Creatures from the sea come regularly to pay their respects (there is a whirlpool)
4	An island with a lake of crystal and glass in the middle. On the full moon shows events from around the world to any who watch (there is a portal to the Plane of Air)
5	Three enchanted islands each home to a different hag of a coven (a dolphin is trapped in something)
6	An island with old stone buildings and a few old hermits that tend to them. A large bronze bell will summon a sea monster (there is a floating barrel)
7	A giant rock with strange patterns and holes carved out of it. Home to a mad but lonely beholder (a storm is approaching)
8	An island with a small harbor and temple to a sea god. Merfolk visit weekly to join the priests in ceremonies and rites (there is the flag of a seafaring nation)
9	A large island with several ships moored there. A group of dwarves or humans is building the start of a colony here (there is a mordenkainen's magnificent mansion)
10	A green island which is home to a small tribe of lizardfolk. They sometimes visit nearby civilization in their canoes (there is a strong wind from the southwest)
11	A rocky island home to many types of seabirds. Two married druids live a peaceful existence on the island (there is a group of flying creatures approaching)
12	A flat island, mostly covered at high tide. Low tide reveals hundreds of entrances to an extensive cave system (it is raining)
13	Several large rocks covered in seaweed. A small colony of myconids tend them (there is smoke from a fire)
14	A cave-riddled stone spire. Home to a clan of seafaring kobolds. They worship a black dragon that slumbers in a cave below the island (there are many crabs)
15	Ruins of an old temple where devils were worshiped. Sahuagin keep a watch on it and will try to sacrifice anyone investigating it (there is a warm breeze from the southeast)
16	A small barren island with a large bright pavilion tent. A group of powerful adventurers rests here and traveled here by magic (there is writing in the sky)
17	A tall island given water by, a decanter of endless water at the summit. Inhabited by shipwreck survivors who worship the flask ()
18	A dormant volcano which houses a tribe of gnomes and their clockwork servants (there are several floating diseased corpses)
19	Permanent mists shroud this island and a several ghostly ships patrol around it. An ancient ruined city lies within (there is an airship flying overhead)
20	A cloud giant castle floating on the sea, whose ruler is magically asleep inside, guarded by elementals (a fog is rolling in)