Open Ocean

The lit surface layer and the twilight under it, off the shelf and over water miles deep. There is no cover and no footing, and a fight here takes place in three dimensions. Below about 650 feet the light fades to permanent dusk, and most of a water world's biomass lives there.

Regional environment Aquatic (water)

Tropical Dry Temperate Continental Polar

Lowland Subsurface

Crossing it

Navigate: DC 12
Forage: DC 13
Notice: DC 10

No cover and no bottom. Position is depth as much as bearing.

In play

Three dimensions

There are no flanks here. A creature with a swim speed can approach from any direction including below, and cover does not exist.
No footing

A creature without a swim speed moves at half speed and cannot take the Dash action. A dropped item is lost.
Twilight

Below 650 feet the water is heavily obscured. Creatures adapted to it see by their own light and treat the dark as their cover.

Variations

Sunlit

The top 650 feet. Lit and warm, and where air-breathers must return to breathe.
Twilight

650 to 3,300 feet. Enough light to see a silhouette against the surface and too little to see anything below.

Worlds it occurs on

Aquan A world that is liquid down to the core, with no land, no shelf and no solid surface to stand on.
Red An Aquan world with an ocean of blood, called the Sanguine Sea, that no two surveys describe the same way.
Terran (Oceanic) A world of ocean from pole to pole, with land only where a volcano has kept up.
Terran (Verdant) A rocky world with liquid water, breathable air and a magnetic field to protect them, rare and the cause of most wars.

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