BIRTH ORIENTATION. “Cephalic presentation at birth is generally held to be advantageous on land as it enables a newborn to breath during labor. Caudal presentation at birth, in contrast, is generally held to be advantageous at sea as it may reduce the risk of drowning. Caudal presentation may also hold an advantage in water, because it orients the newborn calf to swim parallel to the mother rather than away from her.”
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004366