in the absence of a trunk or stone to lean on, a capybara may be an option;
I have observed these two individuals do this twice;
see also
https://www.inaturalist.org/journal/nelson_wisnik/21258-the-friendly-capybara
The Darter catching these fish was an expert we saw him catch at least 12 fish in about 10 minutes, must have been hungry. He was so quick that most of the times we weren't fast enough to get a photo before he swallowed the catch and then down to hunt another one.
European Perch listed here: https://inaturalist.ala.org.au/observations/39823723