Tamsin has weather-browned skin with a fine, all-over stipple of pale sun marks across her nose and forearms. Her broad hands are permanently ridged and toughened from hauling wet rope and stripping reeds; the nails are kept short and stained green at their edges. She moves with a measured, testing gait, setting each foot as if the earth might answer back. Her dark hair is bound in a practical braid threaded with tiny dried seedpods that click softly when she turns. At first meeting, she leaves the impression of someone listening to the ground more closely than to you.

Tamsin is warm toward anyone willing to learn and distrustful of anyone who treats the marsh as empty ground. She jokes readily while working, but becomes stubborn and withholding when the drowned expedition is mentioned. In a crisis she is decisive and generous with her own safety; afterward, she can be defensive about why she made those choices.

Tamsin grew up in the marsh village of Saz, where families mark the changing channels with poles cut from the reeds that overrun every bank. Her mother, Ula, taught her to read water by its smell and the angle of floating leaves. Years ago, Tamsin guided an expedition into a drowned shrine to retrieve a bell said to warn the village of floodwater. She chose a faster route after a sudden squall, and the party became trapped beneath a collapsing reed mat. Tamsin escaped with the bell, but two companions, Oyun and Boro, did not. She has never forgiven herself for leaving them, though she tells herself there was no other way. The bell now lies buried beneath the reeds, where its faint toll sometimes comes before storms. Tamsin protects Saz by guiding travelers away from dangerous channels, but she is also trying to return the bell and settle her debt to the dead. Ula wants her to stay alive; the village ferryman, Naran, wants her to stop taking risks; and a newcomer, Yara, has begun asking why Tamsin knows the shrine's hidden entrance.