Rise and Hide

Rise and Hide: daily vertical migration 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 shoal

In Rise and Hide you are a shoal of small sea animals in a slice of the open ocean, with a real day and night clock. Every night you rise to the sunlight zone to feed, and before dawn you sink to the twilight zone to hide. This daily trip up and down the water column is called daily vertical migration, and it is the biggest animal migration on Earth. The game covers the Cambridge IGCSE Marine Science (0697) points on migration: why many organisms, such as plankton, fish, squid and shrimp, undertake daily vertical migration between the twilight zone and the sunlight zone.

• The sunlight zone is the top 0-200 m of the open ocean. The twilight zone is 200-1000 m, and the midnight zone is below 1000 m.
• A depth gauge on the side of the screen shows the zones, your depth and where you should be right now.
• You play four days, as a different migrator each day: lanternfish (fish), copepods (plankton), squid and deep-sea shrimp.

Why migrators rise at night

The food is in the sunlight zone. Phytoplankton need light to photosynthesise, so they live near the surface, and the zooplankton and small fish that eat them gather there too. That is why the sunlight zone has such a large mass of living organisms. In the game an energy bar drains all the time. Swim through the clouds of copepods, phytoplankton or small fish to fill it. Stay down in the twilight zone all night and your shoal starts to starve, because there is very little food down there.

Why they sink by day

Predators such as tuna, seabirds and small fish like anchovies hunt by sight. In daylight the sunlight zone is bright, so anything swimming there is easy to see. A red danger line shows how deep there is enough light for predators to see you. It sinks fast after sunrise and rises again in the evening, so you learn that light is the trigger: migrators follow the changing light at dawn and dusk. Stay above the line and an eye fills up over your shoal, then a predator strikes. Below it, in the dim twilight zone, you are hidden, and the cooler water means you use less energy.

• On Day 3 a full moon lights the top of the sea, so you must feed below a moonlight line.
• On Day 4 a fishing boat's floodlights show how light pollution can upset migration.
• Copepods are slow swimmers, so on Day 2 you have to set off early.

Read your own echo sounder chart

At the end of every day you see your 24 hours drawn on an echo sounder chart, the way scientists see migration: depth down the side, time along the bottom. Your track sits next to the deep scattering layer, the band of migrating animals that rises at dusk and sinks at dawn, and you score a bonus for the time you spent in the right zone. This is the depth-against-time graph that exam questions often ask you to describe and explain.

Migration in three dimensions

While you hide in the twilight zone, you swim through gates to answer questions about migration in general. Animals migrate for four main reasons: finding food, finding mates, moving to a different habitat to reproduce and avoiding predators. Migration happens in a three-dimensional environment, so it can be vertical or horizontal, and over short or very long distances. Your daily trip is vertical and short (a few hundred metres), while a humpback whale or a leatherback turtle swimming past makes a horizontal, very long migration of thousands of kilometres. Every mistake brings up a short explanation and a link to the lesson, and the recap at the end lists everything you need to remember.