Abstract: A water pump includes a pump body and a block which are respectively provided with attachment surfaces that surround an opening defined by a vortex chamber. A first one of the attachment surfaces is provided with an annular groove. An annular sealing member is embedded in the annular groove. A sealing mechanism for the water pump includes the annular sealing member having a protruding segment protruding from a periphery of the annular sealing member such that the protruding segment extends outward from an outer periphery of a second one of the attachment surfaces; and the annular groove having a branching groove segment which branches out from the annular groove and is provided in the first one of the attachment surfaces such that the protruding segment is embedded in the branching groove segment.