The following graph represents the phase behaviour of water under differing regimes of pressure and temperature.
Now for the transition ice to water...we consider (dP)/(dT)...and this slope CLEARLY is negative (even tho I think this diagram exaggerates the slope)....and consider the Clapeyron equation for phase transitions...
(dP)/(dT)=(DeltaS)/(DeltaV) (this is derived from several state postulates, and at the moment I simply ask you to accept its formulation)…
And if (dP)/(dT) is negative, (DeltaS)/(DeltaV) IS ALSO NEGATIVE... Capisce? But DeltaS for a solid to liquid transition IS CLEARLY POSITIVE. And thus DeltaV is NEGATIVE...i.e. the SOLID PHASE, the ICE, OCCUPIES MORE VOLUME than the liquid phase. This is quite an unusual phenomenon, with the result that ice-cubes, and ice-bergs, FLOAT IN WATER in that they are less dense. And I think this is the result you are asked to consider....
