Fin Control

Fin Control: the external features of fish for Cambridge IGCSE Marine Science

This free game is part of our Cambridge iGCSE Marine Science (0697) course for exams in EXAM YEARS 2027-2029.

Be the fish

In Fin Control you are a young red snapper on your first trip across a coral reef, and your fins are the controls. A reef biologist called Ama has tagged you and follows you from the seagrass lagoon to the edge of the reef. Each fin button does the job that fin does on a real fish, so you learn what each external feature is for by using it. The game covers the external features of fish in the Cambridge IGCSE Marine Science (0697) course: the operculum, scales, the five kinds of fin, the lateral line and the nares.

• The caudal fin (tail fin) gives forward thrust: in the first leg you only move while you hold it down.
• The pectoral fins make the directional changes: flick one out to turn into the next lane, past the coral. They also help to brake and to control pitching.
• Your scales are your armour. Every crash knocks some off, because their job is protection.

Pitching, rolling and yawing

A labelled diagram can tell you that fins control pitching, rolling and yawing, but it is hard to picture what those words mean. In the game, spinning eddies in the water tip you over in each of the three ways, and you have about two seconds to use the right fin before you crash:

• Pitching is the nose tipping up or down. A barrel-shaped eddy lying across your path causes it, and the pelvic fins, the pair on the belly below the pectoral fins, control it.
• Rolling is tipping over onto your side, turning round the long axis of the body. A hoop-shaped eddy round your path causes it.
• Yawing is the head swinging from side to side. A flat whirlpool causes it.
• The dorsal fin on the back and the anal fin on the belly near the tail stick up and down from the body like the keel of a boat, so they stop both rolling and yawing.

The first time you meet pitching and rolling, the fin is folded so you can see what happens without it. In the final leg the eddies lose their colours, so you have to read the axis they spin around.

The lateral line and the nares

In The Murk a storm has stirred up the sand and you can hardly see. Barracudas strike from behind, but your lateral line, the line of pores along each side of the body, lights up as it detects the vibration of the predator moving through the water. Change lane in time and the barracuda shoots straight past. Fish use the lateral line to dodge predators, find prey and swim in schools, even in the dark.

At Dusk you are hungry but cannot see the shrimps hiding in the reef. Chemicals from the food spread back through the water, and your nares, the small nostril openings on the snout, detect the chemicals. Your nares glow brighter as the smell gets stronger, and you steer into the right lane to find the food. The nares are only for smelling: a fish breathes by taking water in through its mouth, passing it over the gills and letting it out under the operculum, the bony flap that covers and protects the gills.

Photo stops: label the fish

Three times on the trip Ama stops you in front of her fish ID board and takes your photo for her guide. You tap each part she asks for on a big side view of your fish, just like labelling a diagram in an exam: the caudal fin, pectoral fin and operculum first, then the dorsal fin, pelvic fin, anal fin and scales, and finally the lateral line, the nares and two parts named only by what they do. Every right answer shows the feature with its function, and a wrong tap explains where the part is and how to remember it.

The six legs

The Lagoon: thrust, turning and a strong current. The Reef Top: pitching and the pelvic fins. The Channel: rolling, yawing and the dorsal and anal fins. The Murk: the lateral line. Dusk: the nares. The Reef Edge: 75 seconds with everything at once, scored with streak multipliers and a bonus for the scales you keep. Every mistake shows a short explanation and a link to the lesson, and your best score is saved so you can play again to beat it.