local depth = 1
local speed = 50

script.Parent.CFrame = script.Parent.CFrame * CFrame.new(0,-depth,0)
while true do
for i = 1, speed do wait()
script.Parent.CFrame = script.Parent.CFrame * CFrame.new(0,-depth/speed,0)
end
for i = 1, speed do wait()
script.Parent.CFrame = script.Parent.CFrame * CFrame.new(0,depth/speed,0)
end
end