The cooling nature of water comes from the high specific heat _and_ the fluid mixing (convection currents, pumped flow, etc). Barnacles and other accretive lif

The cooling nature of water comes from the high specific heat _and_ the fluid mixing (convection currents, pumped flow, etc). Barnacles and other accretive life forms means that the thermal gradient drops sharply, and hence the heat flow rate drops significantly. Take a comparison is between (say) 25C heatsink in contact with 10C water across a boundary layer that likely on the order of 10mm thick, versus what is effectively a static fluid ~50mm thick followed by the same boundary layer. So the unmixed fluid is going to be ~6x [1] thicker, for a heat flow rate 1/6th the original. And that's assuming that barnacles do in fact conduct as well as water, something that's unlikely (water is ~0.6, human flesh ranges from ~0.2 to ~0.5) [1] Insert a bunch of unstated assumption about the fluid flow rate, salinity, etc etc.