I believe this gentleman was digging clams, but it could have been some other type of shellfish or creature. It was in the Fukushima River, an obviously tidal river near where it entered the sea in southern Miyazaki.
What was quite remarkable was that this was 3:30 in the afternoon, the hottest part of the day, in the last week of July, the hottest part of the year, in what is often the hottest part of Japan.
Of course he was dependant on low tide, a factor outside his control, and you can see he is dressed for the conditions...... notice the reflective sheet covering his back and shoulders,.... but I can tell you it was blistering hot
I had left Obi castle and the surrounding samurai district and caught the train back to where I left the pilgrimage and I was heading to Shibushi, a little further west along the coast.