Drag sideways anywhere (or move the mouse, or ←/→) to steer the lure.
Going down: for the first 1.5 s nothing can bite (the lure glows with a ring), so you can get a feel for steering. Then slip past fish. The first fish you touch bites and starts the reel-up, so the deeper you get, the richer the water.
Coming up: steer into fish to hook them, as many as your hooks hold.
Strings: fish of one colour hooked in a row form a string, and every fish in it pays × the string's length (up to ×6). A different colour in the middle splits it.
Light the pier's quota lamps (500 points each) every cast, or lose a lantern. 3 lanterns.
Head start: every lamp lit past the quota starts the next cast 10 m deeper.
Once every hook is full, the line reels in 2.5× faster.