This would be unlikely to occur as animals move up and down in the water column on their own.
(This; would be; unlikely to occur) (This; to occur; T:as animals move up and down in the water column on their own) (animals; move; up and down in the water column on their own)
This This animals
would be to occur move
unlikely to occur
T:as animals move up and down in the water column on their own
up and down in the water column on their own