Current or former Navy... Will I have to participate in the pollywog/shellback ceremony?

to NOT do so would be an insult to all those who have gone before you. and shameful as a member of the US Navy to avoid participating in such wonderful traditions. you would be ostracized, made fun of and lose a helluva lot of respect.

DH was in his 30s when he Crossed the Line and transited the Ditch the first time.

and God Forbid you ever make E7 and decide that partipating in those traditions is beneath you.. you would l NEVER be considered a Chief regardless of your paygrade.

It's a right of passage. Of course, it is your choice to not participate, but I am sure that what you have heard happens is MUCH worse than what actually happens. It's not anything bad. It is just silly, and is a good way to break up the monotony of a normal deployment and commemorate crossing the equator. Just go along with it. They don't do anything to hurt you. There is usually a talent show, a contest to make silly costumes, doing some situps/pushups while being sprayed with water, and some other things. It's really not a big deal.

Its optional you pussy.