[gizmofixer]

i've had/have a lot of turtles and have never seen a turtle egg that large.
even giant snappers dont make em that big.
most turtle eggs (including the ones you have) will be no larger than the last digit of your thumb.
i've hatched turtle eggs laid in the water, they're usually good for about 2 days, no more.
this is because the embryo attaches itself to the shell and must not be moved or jostled after a few hours.
my guess is a bird of some sort.......