Certainly, no one in their right mind would build a catamaran in steel; however, there are any number of aluminum cats out cruising the oceans, mainly made in Europe (and usually France).

As Bob Kingsland's picture of "Gringo" vividly shows, metal boats can bend or stretch considerable upon impact, instead of breaking and shattering.

To see what I mean, have a look at a closer-up picture of "Gringo", with the HUGE dent in her side after being struck --but still very much floating. http://www.boatdesign.net/forums/attachments/boat-design/18059d1199668116-steel-yacht-construction-steelhull.jpg

Here's another illuminating picture below, this one is from http://www.yachtdesign.com.br/01_portugues/noticias/artigo2.html

Bottom line is, of course, that there is no ideal boat building material; and that the level of build quality is very important for any material, be it wood, fiberglass, etc. I've built in three mediums --steel, fiberglass and wood. Certainly, many people build in steel because of the relatively low cost and ease of construction (but it depends on one's skills as a builder and finisher, and there are many poorly built steel boats around), and also since it can be hard to find good, used, and affordable used steel boats, they make them themselves. But, certainly, no one should delay going ocean cruising because they don't have a metal boat! If the history of going to sea shows anything, it's that boats of every stripe have made successful cruises. However, a metal boat can provide an added level of security in terms of ruggedness (grounding or collision), lightning protection, rigidity/resistance to oil-canning and flexing in heavy seas, and for those who venture into colder waters insulated metal hulls tends to provide good heat retention. There are many pros and cons to various building materials. But, for me, in my commercial career, I've seen some metals boats in highly compromising situations that would've seriously damaged other boats. All this being said, I've raced on some fast boats, local racing that is not offshore, and I enjoy sailing fast. However, for me, when cruising, an extra day or so on passage because the steel boat might go as fast, is no big concern to me. (But many fiberglass cruising boats can't keep up to a J boat anyway!)

Would a metal boat have survived being "attacked" by whales, which seem to have caused the rudder to come out and probably broke the prop shaft's shaft log from the hull on the J boat (that's my suspicion as to why it sank so fast, a major ingress of water and not just at the rudder post)? My guess is yes. Again, however, I'm not advocating for one "ideal" building material for all situations or cruising areas. I'm just pointing out that the strength benefits of steel or aluminum construction are often pooh-poohed by those who contend that excessive weight or excessive maintenance rule them out as good building materials (however, I have never built in aluminum so don't have first hand knowledge of it) and outweigh the benefits. It's a multifaceted topic with no "easy answer", but my gut feeling is that a metal boat, properly constructed, would not have suffered extensive hull rupture from a similar whale attack (and yes of course such attacks are unusual !).