According to Lechatelier principle, freezing of water is favoured at

${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \rightleftharpoons {\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right),\mathrm{\Delta H}=-\mathrm{Ve} ;$ 

Reaction is exothermic . . .favoured at low T ;

Reaction involves increase in volume ( density of ice is less than that of water) . . . favoured at low P.