WRECKERS! — you keep the last light on the shoal.
Hold ◀ ▶ to turn the beam. Let go and it stops.
Hold the light on a white trader until it sees you — it turns for open water.
Red raiders steer toward the light. Leave them in the dark and they lose the shoal.
Anything that reaches the rocks costs you a lantern.
From wave 3, sharks stalk the shoal — catch one in the beam before it reaches its prey.
From wave 4, mermaids swim in — keep the light on them all the way to the lighthouse for a big bonus, and keep sharks and raiders away while they're dark.
A shark that kills a raider, or a trader you just saved, may drop a supply — catch it in the beam to reel it in. Fill all 4 slots and hit the middle button to unleash the Light Wave: it shoves every ship off the shoal, scares every shark, and pulls in every mermaid at once.
Clear a wave with a lantern missing and you get one back.
Every 5th wave, a Kraken looms in from the side. Keep the beam on it to hold its aggression down — let it go dark and it creeps closer, and if its arm reaches the lighthouse, the light goes out instantly. Every mermaid you've saved swims out to shove it back, and the Light Wave halves its aggression outright. Hold it off for the wave and it flees.