What about cruising and scuba diving? This question for certified experienced divers. Do you suggest bringing you own dive equipment such as regs, body suits, masks and fins and only rent the tanks at which ever location one chooses to dive??

I highly recommend that. You know that your equipment is maintained properly. You know that your equipment fits properly. We take our own snorkel gear and used to take our diving gear. Snorkeling is much less hassle and easier for us now. Best wishes and have a wonderful cruise!

Just to offer a little different perspective here,
I've snorkeled all over (Hawaii, Mexico, California, Caribbean) and never had a problem with the gear provided; and for me, it sure beats dragging all that bulky stuff along.