I do not doubt that it is possible to dive the Cathedral without going into deco, however, in the many times I have gone to that site with at least four different dive ops, the path taken through the site has invariably been through several swimthroughs with the last one being the big one that gives the site its name, and coming out of it deep with a deco obligation. When I was younger that sort of thing did not bother me, but these days I do not do deco diving any more, and I don't dive as deep as I used to.