Are you looking for storage on land or on your boat? The answer will potentially lead to different approaches.

On land - hard containers (multiples of the same for stacking, etc) will be an option. On water - you might will be better served w/ soft containers you can put in small areas (under bunks, small closets, nooks and crannies, etc). There a many different types of water proof containers available. It all depends on your needs. I would not trust my valuables to "ziplock" bags. They are not sturdy enough, IMHO, to stand up to the rigors to life at sea. You might chack into some cruising forums to get ideas from them for onboard storage.

One item I would recommend is ALOKSAK (www.aloksak.com. I have used some of their smaller bags and have been pleased. (Disclaimer - No, I have no affiliation w/ them.) Just some things to consider.