Hi, the Museum exhibits are up to 12m underwater so are really best seen by diving. Most people can be safely taken to such depths by competent dive schools ( and Dive College is certainly competent and safe). Suggest you call them and then consider a try dive in their pool or close to the dive centre before you try the Museum. You don't need to be a strong swimmer as the buoyancy aids and fins will help, but you do need to be confident.