Ganymede seems to acquire several ocean layers, stacked up with levels of ice between them. The very best level of ice would be the crust, which might be about 150 kilometers (about 90 miles) thick. The bottom ocean stage could be 800 kilometers (about five hundred miles) down below that, https://moons26047.thenerdsblog.com/40569452/new-step-by-step-map-for-moons