Throw a stone into water and it sinks.
If you throw a stone into water, it sinks, OR it'll/it will sink.
We're lost because we didn't look at the map.
We wouldn't be lost if we had looked at the map.
It won't rain tomorrow and I'll go to the coast.
We’ll go to the coast tomorrow unless it rains.
He's very ill so he isn't at work.
Unless he was very ill, he would be at work.
