Source: The Great Interpretation of Dreams (Ibn Sirin)
(By analogy with large fish and predators) A shark may indicate a strong, dangerous enemy in the water (symbol of the world or authority), or great sustenance that comes with risk.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
(By analogy) It may indicate a man of authority, power, and might, or a dangerous thief.
Source: Signs in the Science of Expressions (Ibn Shaheen)
(By analogy) It is interpreted as a strong enemy or looming danger. Escaping from it is salvation from evil.