I did a search for "Dolphins", and later via the "Dolphin" tag, while exploring the new site and noticed it did not turn up one particular image I was looking for. It was only via uploading the image that I discovered the original, which is correctly tagged under Dolphin.
Full Search: https://wallhaven.cc/search?q=id%3A1963&categories=111&purity=111&sorting=relevance&order=desc&page=2 (Currently returns "28 Wallpapers found for dolphin" as of 2019-06-06)
Image not found in search: https://wallhaven.cc/w/011zp3