I saw a sewer worker diving into a sewer in Old Delhi. The road was flooded, and he went down holding the end of a rope in one hand. He reappeared less than two minutes later, breathed deeply for a few moments, and went down again. After his third dive, the water began to go down, so he’d managed to unblock something, but he went down again twice more. I didn’t stay much longer; the last time I saw him he was sitting on the edge of the hole with his feet dangling. He was soaking wet of course, and disgustingly filthy from head to toe. His (female) co-worker was coiling up the rope, so I guess he’d finished the job.
No equipment of any kind apart from that rope, and no special clothing.
Apparently dozens of people die doing this job every year in India.
I’ve cleared blocked sewers myself, in England and in Scotland – usually just pipes, cleared with rods; once by digging up a drive when there was an obvious, new depression in the surface at just the distance where the rod refused to go any further. Renewing the ancient brickwork was the hardest part of that job, but not the most unpleasant! But diving into a flooded sewer? No thanks!