Sforno on Exodus 8:8/ספורנו על שמות ח׳:ח׳

1ויצעק משה אל ה' על דבר הצפרדעים אשר שם לפרעה, Moses prayed that G’d remove only the crocodiles which had been sent against Pharaoh and his people, whereas any others should remain in the river. It required a special prayer, here described as an outcry, to ask G’d how to arrange the removal of this plague.