With more than a thousand ships in Singapore's waters daily, and maritime trade accounting for about 7 per cent of gross domestic product, keeping sea lines open is critical to the Republic's prosperity, said Coordinating Minister for National Security K Shanmugam on Friday (Nov 28).«The environment is congested and it is challenging. You look at the number of ships that fall into our waters — more than 1,000 ships calling and transiting,» he said.«One of the ways in which (we) can be attacked is through an attack on ships in our waterways, or an attack from the sea on Singapore itself,» added Shanmugam, who is also Minister for Home Affairs.He was speaking to reporters on board the navy's Independence-class littoral mission vessel RSS Justice after observing Exercise Highcrest, an annual inter-agency exercise — held from Nov 24 to 28. Read more