Did something happen in the previous bath. Can you takea bath with him?

Could have the water been too hot or too cold? If they were older I would suggest May be enjoy washing hands in a deep sink with bubbles and toys and encourage water play to realise water is fun. But in your case as your child is small I would sponge bath them for a while and hopefully it will be forgotten about and you can start again. But with winter fast approaching make sure the room is nice and warm, so it is a positive experience.

Maybe change some of the products used during bath time; possibly some sensitivities?

Maybe try putting him on his belly over your arm instead? My boy didn’t like being in the bath on his back but if I turned him over, he loved it basically turn your baby over, hold one armpit/shoulder and put their arms over your arm so that your arm is across their chest – I hope that makes sense!!!

Check the water temp, check his skin if he has dry skin or nappy rash that could hurt and associate the pain with the water. Other than that its either the soap or has had a scare (water on face or slipped in bath) and associates that with water.
My youngest hated water for so long. We got him through it by showering.

My son did a similar thing, so he has been having showers with either myself or my husband. He is 3yo now & still prefers a shower.

Is it cold where you live? Maybe he’s going from really warm to freezing cold then the water warms him up again. I think might be that the water is too hot for him? Just a suggestion and i’m in no way saying you aren’t a good mum, just thinking of all I can to change how he feels about water. Did he get water on his face? That might make him dislike it, he might have breathed in water if his face got wet.

Maybe he’s just cold when he undressed and then putting him in the warm water he’s not liking the quick change in temperature ??
I would still carry on with putting him in the bath/shower but keep him warm and wrapped in a towel till the second you put him in the water.
Good luck.