Why destroy Laketown's bridge?

[davem]

Originally Posted by Sauron the White

It means that Smaug did not like water. So its easy to then see that he would want to be as far away from it as possible. Thus, an attack for the air was his preferred mode of attack and would not land being closer to the water.

Happy now?

Amid shrieks and wailing and the shouts of men he came over them, swept towards the bridges and was foiled! The bridge was gone, and his enemies were on an island in deep water too deep and dark and cool for his liking.

In what way, then, was he 'foiled' by the destruction of the bridge(s)? The implication is that he couldn't get to his 'enemies' as he first intended - because they were on an island in deep water.