What stresses most snakes about soaking is (1) the unusual circumstances- doing something they aren't used to & didn't enter on their own, & (2) the loss of
traction- bathtubs are slippery-smooth & that unnerves most snakes...even mud puddles have texture.
A towel in the water is one of many options...
FYI, it's been a long time since I've had any stuck eye-caps to deal with, but once the snake is well-hydrated (from soaking, etc) & then dry, I have used a bit
of tape (package tape, not duct tape!) to gently stick to the eye-cap & remove it...it's much safer than trying to use fingers or tweezersin such a delicate
area. Not promising that several layers of eye-caps will come off easily, but using a bit of tape is pretty innocuous to try, IMO. It's a challenge to restrain any
snake while you do this...a second person to help handle really helps.