DS refuses to sit down in the tub

In July, when we were away on a family vacation, DS refused to sit during his bath. At first, DH and I thought it was because DS was in a "foreign" tub so we didn't push the issue, but it's now November, and DS continues to stand during his entire bath!

DS enjoys his baths and bends over/squats to play with his toys, but he absolutely refuses to take a seat. When we ask him nicely to sit, he politely refuses! And when we try to plop him down, he stiffens his body and screams (we don't use this approach too much for fear he'll slip and hurt himself).

Any suggestions on how to get DS to sit in the tub would be greatly appreciated!

TIA.

We had the same problem. Repetition is what made him stop.
Every time DS would stand up, we would say "Please sit in the bathtub" and gently sit him down (DS didn't fight back too hard, but would get right back up every time).
If DS stood up more than 3 times, that would be it - bath over.
We would say "I guess you want out" and take him out (even if he just got in).
After a few days (it might take longer. DS was 12 months old) he came to expect this and decided it was not worth it to stand, since it wasn't getting him anywhere.
The key was being calm and consistent.
Now he only stands when he is finished, because to him, that means out.
Encourage him back down if you can, or just end the bath telling DS what is happening.
He will get the message.
I hope this helps or gives you some ideas,