Student or Learner
When we are on the beach and the water of the sea is freezing cold, can we say?:
This water is colder than ice.
Is it a common expression in English language?
This is a hyperbole you might hear from a child. It's not a common expression.
More common (also exaggerations) are 'This water's like ice'; 'It's icy cold'; 'It's as cold as ice'.