Final answer:
The central idea about rescue at the water edge can involve heroic actions and the struggle for survival in dangerous situations.
Step-by-step explanation:
The central idea about rescue at the water edge can be seen through various passages from different texts.
For example, in the passage 'Imagine that there's a fire in a building nearby' the central idea is the heroic actions of firefighters rescuing victims from a dangerous situation.
In another passage, the central idea is the struggle for survival in a life-threatening situation, as seen when the characters are trapped in a boat and try to reach the shore.