a submersible heat - exchanging apparatus comprises a cylindrical heat - exchange component configured with one end for sealingly engaging a terminal plug and the other end for sealingly engaging and communicating with a coupling manifold having opposed inflow and outflow ports . a flow - directing elongate insert is provided with one end configured to engage the coupling manifold interposed the inflow and outflow ports , and the other end provided with an aperture and configured for abutting the terminal plug . the flow - directing elongate insert is configured to slidingly contact and cooperate with the inner walls of the heat - conductive conduit thereby partitioning the heat - conductive conduit into two opposed fluid transmission channels wherein one channel communicates with the inlet port and the other channel communicates with the outlet port . the coupling manifold is configured to sealingly engage an aperature provided therefore in a fluid - containing receptacle whereby the heat - exchange component extends into the receptacle .