def update():
for primitive in fish_of_the_primitives1:
moveObjectBy(primitive, 0, - 100)
for primitive in fish_of_the_primitives2:
moveObjectBy(primitive, 0, 50)
time.sleep(0.45)
for primitive in fish_of_the_primitives1:
moveObjectBy(primitive, 0, 50)
for primitive in fish_of_the_primitives2:
moveObjectBy(primitive, 0, - 25)
onTimer(update, 500)