One example of dramatic irony is when the people on the shore see the boat out at sea. They believe that it is a novelty, not that someone might need their help. The people in the boat, see the people on the shore as their rescuers. Both are wrong.
Another example, though not as strong as the above, is when the men are bailing water from the boat and they say that they'll get ashore if the 'wind holds up'. Well, this is ironic because it is the wind that got them to this point of death in the first place.