As well as quarrying on land, 21% of the sand and gravel we use in England and Wales comes from the seabed around Britiain's coast, where the aggregate is extracted by special ships called dredgers.
Q: How much marine sand and gravel do you think was extracted from English and Welsh waters in 2007?
Click back into the vote archive at the beginning of next month and read the commentary to find out the correct answer!