Zoey

Marie

Ignacio

Galen

Ollie

Tala

Quinn

Bodie

Teacher

British

Vampire Bodyguard

Francis

Woman

Bodyguard

The Narrator

African lady

Soft Bubbly

Southern

Robot

Hailey

French

Hood

Indian Girl Accent

A French Girl

Male Russian Accent

Irish

The River Person is a hooded figure who provides transportation services to Snowdin, Waterfall, and Hotland on their wooden boat for the Underground. Sometimes, their boat has the face of a dog and runs on top of the water.
The River Person is shown to be calm, knowledgeable, and tends to enjoy sometimes joking with the protagonist (Frisk). They don't seem to care if there is a Genocide Route in progress.
The River Person's gender is not decided, and they even dismiss it as not mattering.

River Person

A calm Monster with a dog-like boat. (Undertale)