Identifying the Classic "Little Fish vs. Big Fish" Computer Game

You're likely thinking of "The Incredible Machine" series. While not exclusively a fish game, its iconic "Fish" puzzle featured a tiny fish navigating obstacles to avoid a giant shark — matching your description of starting small, facing larger threats, and choosing evasion.

Why It Fits

• Start as small fish: Player controls the tiny fish.
• Challenge bigger creatures: Shark is the primary antagonist.
• Choose to run away: Puzzle-solving revolves around avoidance/navigation.

Other possibilities include Feeding Frenzy (eat smaller fish, avoid larger ones) or Ecco the Dolphin (though you play a dolphin). If "The Incredible Machine" isn't it, provide more details: approximate year, platform, graphics style, or specific mechanics.