Graph of the speed of sound in water vs temperature. Tabulated values (circle markers)  from "The Engineering Toolbox" <a rel="nofollow" class="external autonumber" href="http://www.engineeringtoolbox.com/sound-speed-water-d_598.html">[1]</a>. 
Smooth continuous line is a 3rd degree polynomial fit (see below) calculated on the tabulated data, accurate within 0.1%.
K. Krallis, <a href="//commons.wikimedia.org/wiki/User:Sv1xv" title="User:Sv1xv">SV1XV</a>
CC BY 1.0
<span class="int-own-work" lang="en">Own work</span>