This bird seems like a glossy ibis with a "pink filter" applied. the dark crown and front are things I look for to find glossies and the structure of the border skin on the face seems normal for a glossy, but its all washed in pink.

The picture quality was bad due to the birds being in the middle of the lake. They kind of had the shape of the duck but seemed to big. They also were not seen swimming. They were quite large. They had a curved neck and a thick body. Noticeable tail and the bird was all black or possibly dark brown.