I think this is a white-faced ibis. According to my bird book, Jim Denny’s A Photographic Guide To The Birds Of Hawai’i, it is an occasional visitor and all reports have been of juveniles or birds in non-breeding plumage. It also notes that it is very similar to the glossy ibis, but doesn’t include a listing for that bird in the book. So I’m going to stick with the white-faced ibis identity unless someone has a better idea.
This one was wading in the shallow of the lagoon behind the beach at Kaloko-Honokohau National Historical Park. The yellow float was one of several isolating an area where restoration work was taking place. The lagoon is a popular spot for many birds, both endemic and visiting.
For more information about Kaloko-Honokohau National Historical Park, go to https://www.nps.gov/kaho/index.htm or bigislandhikes.com/kaloko-honokohau-park/.