"Proper Etiquette" states your mother should not throw the shower. U may find this site quit helpful etiquette.com - they are great to ask for things you are unsure of.
Also, if it were me, I would ask seriously who is planning the party. Let them know while you appreciate, the offer this is something that is distracting to you and not what you envisioned for the time surrounding your wedding. I don't care for being the center of attention either and would feel extremely uncomfortable - not just on that day but the stress/build-up surrounding it. Make sure they hear your wishes and know they are not meant to hurt them - which I'm sure u would. Sometimes people "hear"what you say but don't think you really mean it and they don't want to let you down. Let them know that is not the case.
Now if you decide to go with the shower remember most cannot stand showers. So think of making it a couples shower. I threw one for my girlfriend and it turned out fabulous This past weekend I threw a baby shower for my girlfriend - also couples. To entice the men i sent the invites in a bottle w/ a cork (not a baby bottle) with a message rolled up inside. Inside the bottle i also threw in some sand and a few seashells. On the invite I but something about Jimmy Buffett, Reggae, and BBQ. 55 people showed - it was awesome. I guess what i am trying to say is if you add a "spin" to it you won't be so much the center of attention as people will be laughing , talking, eating, doing other things besides waiting for it to be over.
hope that helps. I must say though I love the scuba gear idea. That is the best yet.
The best defense is a good offense so hand them the mask the minute you see them. Drinking from a snorkel, hmmm, that could be a fun party game! Balance a ping pong ball on a snorkel and walk an obstacle course--man am I ever evil!
