Injured Duckling Help

[breckash]

My son is a boat captain and found this little duckling floating solo in the middle of the ocean on Monday. Having chickens, he called me to come and help. We have been keeping the area clean and moist (Neosporin) twice a day, and then feeding him and keeping his bedding super clean. The wound is odd, as it never really bled, except in one small area up under the skin flap. Otherwise, it looks the same as the day we got him, expect a bit more "yellowish" compared to the day we found him. Just wondering if anyone has any advice as to what this could be. Is it an injury or a possible birth defect? And how does it seem to be healing? He is eating and drinking and walking around. Pooping fine, too. Any advice would be helpful!