Sandbanks are areas of sand in a river or sea, especially dangerous because they are just under the water and can make boats crash.
Sandbanks can be dangerous for boats, so people need to be careful around them.
Examples:
The boat got stuck on a sandbank.
We need to be careful of the sandbanks when we go swimming.
The sandbanks are just under the water.
The sandbanks are like a secret trap for boats.
The sandbanks hide under the water and surprise the boats.
The sandbanks are like a hidden mountain for the boats.