A cloud of Bloomspawn is a drifting glow in the water, as wide as a village green, turquoise at its heart and silver at its edges, slowly turning in the current. Close to, it is made of countless specks, each the size of a grain of sand, some round and clear like fish eggs, some tiny wriggling fry, some threads of seed. The cloud pulses gently in light. It makes no sound itself, though the Tidesingers' song carries through it. The water inside it tastes of salt and something sweet, like rain.

They drift in the warm currents across the plane, in a few great clouds and many small ones, and the Tidesingers lead the largest along known paths between their coral cities.

Bloomspawn have no will. They drift, feed on the light and the warmth, and grow, and specks fall out of a cloud as fry and swim away, while new spawn gather into it from the plane’s creatures. They move with the current or with the Tidesingers' song, which they follow as a flock follows a herder.

Life in the Surging Deep heals and adapts, and Bloomspawn are that life at its most concentrated. A body that passes through a cloud has its wounds closed and its sickness eased, and the longer it stays the more the cloud does. It also changes: a swimmer who lingers grows fine gill-slits, a webbing between the fingers, a tolerance for the deep, as the plane’s Law of Adaptation works faster.

A cloud lasts as long as there are creatures to spawn into it. It thins in cold water, and a cloud driven into a cold current scatters and is gone. The specks that leave it become the plane’s fish and creatures.

The Tidesingers bring their sick and wounded to the clouds, and travellers who come seeking healing are often taken to one. The cost is change: a traveller who bathes too long comes home healed and slightly altered, and some never quite want to leave the water again. The predatory Undertow Rays feed their young in the clouds, and the Tidesingers guard them for that reason too.

On the Material Plane healers near Water-Gates tell of "the bloom", a glowing water that cures, and some baptismal rites are said to call on it; what such water does on Caeldon, if anything, is disputed. Tales confuse the clouds with the Life-Bearers, which carry life’s seeds to new worlds; the clouds stay in the Deep (see Knowledge of the Cosmos).