Had a HUGE problem with Kyle for a long time - she was practically hydrophobic.
I tried a towel in the bottom for grip, I tried a sponge to hang on to, I tried leaving my hand in there with her, I had Tsam in there to show her it was safe for dragons, I got in the
bath WITH her, I tried her in smaller containers (sink, glass bowls etc), I tried lower water... I have it to the tops of her TOES and she'd STILL freak out.
So eventually I gave up. I ran a normal dragon-sized
bath for her, dumped her in it and told her to get on with it. I watched over her for half an hour, occasionally topping it up with warm - and she finally relaxed and put her feet down.
She's now three years old and still occasionally freaks out about the water, but I just let her get on with it. She soon calms down when she realises her feet are on the floor!
Try all the above tactics. Failing that, let the silly beast freak out for a bit.