sun fish

I was going across the south bay when I saw this strange fin sticking out of the water but I could not get close enough to it to see what it was, every time I got my boat close to it, it would go down. My husband came along and pulled up to me and asked if I was broke down, I told him there was something here but it was down at the moment. It came back up and he told me to get on his boat and he would use his trolling motor to get me close enough to see what it was and take a picture of it. it is a sunfish, it is sad that it was in the river, they live out in the deep ocean and only come in the river when sick or to die.