What do you mean by anomalous expansion of water?
The expansion of water when it is cooled from 4°C to 0°C is known as the anomalous expansion of water.
When a given mass of water is heated from 0°C to 4°C, it contracts, i.e. its volume decreases.
On heating from 4°C to 10°C, it expands, i.e. its volume increases.