On the Nature of the Seas and Oceans

Hidden under water are myriad realms, unseen to surface eyes.
The shallows are home to abundant reef systems, dense kelp forests, and luscious plains of sea-grass. Here are found the many realms of what are though of as sea-folk; Mer-folk, Merrow, and most other ocean-dwelling peoples that approximately match the humanoid phenotype. There is great variety among their settlements; these communities are far more suited what land-folk think of as nomadic lifestyles, but permenant habitation sites range from cave-systems to sprawling metropolises.
Stony and sandy wilds dominate the mid-depths. Great moutains unkown to land-dwellers rise around the Durathoss; some that breach the surface and are thought of as simple "islands", while others remain shrouded by water, their majesty reserved for the creatures of the seas.
The deepest regions are the territory of the largest creatures; leviathan, dragon turtle and kraken. Even the sea-folk are reticent to explore these regions, for fear of straying into the dominion of a protective behemoth.
Many an inland sea or lake is joined to the wider ocean system by a deep channel. Land-locked salt-water is a strong marker of this, but examples have been found of freshwater bodies with such a connection to the wider ocean, usually where the lake is fed by a vortex from the plane of water.

Ocean Travel

The appeals of shipping heavy or valuable goods across open ocean are offset by the great risks to cargo, craft, and crew. Crossings of deep ocean, even with an escort of sea-folk, are considered too dangerous for general use because of the exposure to total loss to the oceanic behemoths. Natural phenomena, caused by improper veneration of the relevant deities, also pose an existential threat to shipping attempts, as do the rare reports of encouters due to Oceanic Cankerous Fissures (see below). Even in shallower waters, there are a great many threats to oceanic travel. Though many near-costal sea-folk enter into arrangements with land-folk for safe passage, or even escort, there is a perpetual risk of roaming banditry, or agitated sea life.
For these reasons, overland trade is still considered the most secure option. Where value, security, or urgency permit, teleportation magic might be procured, but these are the rarest of cases. Oceanic trade is generally limited to coastlines and island chains, and os usually comprised of convoys of shallow draft barges - often the same craft that are used in river systems - which may either be delayed by, or lost to, adverse conditions. Larger ships have been used to transport bulk or precious cargo, usually under heavy escort.
For exploration, there is little recourse but to use an ocean-worthy craft. Ome undertaking such a venture should hire the most experienced senior crew possible, pay abuntant homage to gods and locals for safe passage, and hope that the dragon turtle is elsewhere.

Oceanic Cankerous Fissures

The denizens of the world's oceans speak of its cankerous fissures in hushed tones. From what little knowledge has reached the surface, these channels bear some parallels with those found in surface regions, but there is a key difference is in scale. In conventional medical wisdom salt water is thought of as a cleansing agent, but not so with The Canker. Apertures found in the ocean are reported to be consistently wider, with a typical oceanic fissure thought to be more than ten times larger.
Some fissures are entirely filled with water, although tainted with brackish pollutants and toxins. These may either be stagnant, or outflowing - the latter bear similarities with connections to an (outflowing) vortex from the plane of water, but for their foul nature. Far more dangerous are the fissures that are not water-filled; such fissures cause strong inflowing currents, which pose a great risk to marine life in the vicinity and cannot easily be distinguished from an (inflowing) vortice to the plane of water. No verifiable accounts of explorations have been recorded. Divinations following the losses of ships at sea of found connections to Cankerous Fissures, suggesting that perhaps these phenomena can drive rip currents capable of dragging vessels of any class into the depths. These propositions are unproven.
Cankerous Vagrancy combined with the Voraguan oceanic environment, means that monitoring and guarding such fissures is a great trial for even the doughtiest of sea-folk.

Type

Ocean