The horizontal lines make it possible to keep that duck swimming flat on the water rather than swimming uphill, a rather unnatural position unless the duck is swimming in waves.
(The horizontal lines; make; it possible to keep that duck swimming flat on the water rather than swimming uphill, a rather unnatural position) (that duck; swimming uphill; ) (a rather unnatural position; is swimming; L:in waves)
The horizontal lines that duck a rather unnatural position
make swimming uphill is swimming
it possible to keep that duck swimming flat on the water rather than swimming uphill, a rather unnatural position
L:in waves