Yes, to a significant degree beauty is in the eye of the beholder. On the other hand, esthetics may not be completely subjective. While standards change from time to time (consider the more rotund female form that was generally considered ideal a couple of centuries ago), there may be some constants. In terms of sailboat design (if not necessarily the female form), let me propose the following:
1. Balance. A design should have balance between the various elements of its design - ie, length, freeboard, height of coachouse, overhangs, etc. in order to avoid appearing top-heavy, or squat, or fat, or too slender, or...
2. Sensuous curves rather than excessive angularity seems more 'organic' and in better harmony with the natural environment
that a sailboat must not only survive in, but make use of.
3. Where possible, angles should be consistent (or at least complimentary) throughout in order to maintain some 'flow' and some degree of 'symmetry' in the design. For fear of offending I don't wish to single
out any particular sailboat designs, but in the world of automobiles I think the Pontiac Aztec is an example of a design which went wrong because of offending this 'rule'.
Are symmetry and balance (and sensous curves) purely subjective preferences? Perhaps, but many of these same attributes are also considered important in assessing attractiveness in the opposite sex (and therefore in the process of selective breeding). What is more, studies have indicated that the greater the symmetry in the human form, the healthier the individual is likely to be.
In my opinion, while function should be the over-riding consideration in the design of any boat, there are nevertheless ways in which a 'practical' design can be made more or less attractive. Furthermore, just as there are ways in which clothing
patterns and colours can mask elements of a less than ideal figure, the naval architect can also mask elements of a yachts design to make them more esthetically pleasing - eg. to reduce the visual impact of high freeboard with a wide sheer stripe. Simply put, the good naval architect strives for function, but does not overlook form.