Chaser

Enemy lurking beneath the ocean, in one of the grid squares; tap a grid location to drop a bomb on the enemy; if you miss the target, the sonar reveals potential location on the last outer periphery. Whenever the enemy is hit, you move through the levels, with increasing difficulty: sonar fading or breaking, enemy relocating, and limited fire. In each new level, the enemy relocates to a new stationary position, but from level 6, it starts relocating within the same level as well.
-In level 2 through 4, the sonar fades progressively
-In level 5 the sonar dies on the 7th shot.
-In level 6 the enemy relocates every 5th shot
-In level 7 the enemy relocates every 4th shot
-In level 8 the sonar is steady but the enemy relocates every 2nd shot and only 30 shots are available