As was true in Egypt's plagues, this description is to be taken literally if it is to make any sense. The second trumpet blows and judgment upon the sea follows, one-third of which turns to blood. The exact mechanics of the judgments are not given by God, but the results of these catastrophes which are seen by those on the earth are extremely real and indicate the literalness of these events. Trying to interpret these judgments as changes in governments, ideologies or economies would not have this kind of effect upon men. People actually die as this happens.
Wormwood speaks of a bitter herb.
When this divine judgment falls upon these final sources of water for the peoples of the earth, incredible hardship in the form of thirst comes to all. Note once again the cause and effect. The nature of the judgment can be determined to a considerable extent by the impact it has upon those who experience the event. The fourth trumpet heralds the Lord's judgment upon the heavenly bodies. Of course He can.