If the specific heat capacity of water were smaller than it is, it would mean that water would absorb less heat for a given temperature increase. This would lead to the following effect:
The oceans could absorb less heat, leading to greater swings in temperature on land.
With a lower specific heat capacity, the oceans would not buffer temperature changes as effectively, resulting in more extreme temperature variations on land as they would release or absorb heat more rapidly in response to changes in temperature.