Not too bad Peter, here are my comments (please don't take them as -ve, more constructive and it's also just my personal tastes too..)
Ref the design -
1) Your bow line (in profile) has a kink at the knuckle - would look much nicer (imo) if it was smooth. I usually spend a complete day just modelling the hull/bow, it can be a really tricky area.
2) The bulwarks around the fore deck look a little high, I would try to keep this at 1m or a little more (so maybe raise your foredeck instead of dropping the shear line).
3) The top side of your hoods look a little feature-less and are possibly too chunky up forward. One way to combat this is to keep a sleeker/shallower hood line and where you need to keep a 1m height bulwark (for the walkways) just model in a local 'upstand' that blends back into the hood.
4) I personally think that your hoods look too elongated in plan too. I think if you use the shape that you've got for the sundeck bulwark (more of an arc shape) and copy that down for each hood.
5) Possibly some sort of 'styling relief' lines along the coaming sides (on the tiers above the main deck) or reduce the height of the bulwarks and then make it back up with some nicely styled railings, maybe teak capped??
6) The heli pad looks a bit too small, I think it could do with a little more length imo.
7) The aft overhangs don't seem to line up as nicely as the front hoods and the angle of the transom 'pod' seems to fight with the other lines in that area.
8) I would have the transom platform wrap around the side of the hull and travel forward untill just fwd of the garage doors, this will act as a handy fender.
Ref the rendering -
1) The water is nearly there, I like the bumps and the colour variation you've achieved but think the reflection needs tweaking - possibly just use a strong fresnel reflection only.
2) In the lower camera shots add some (but not too much) fog/atmosphere to the horizon so that it gives you a sense of depth.
3) In the higher camera shots your false horizon looks out of place - let your sea extend as far out as possible.
4) Find some nice cloud textures to use as a background environment - this will also help with reflections.
5) Try not to loose too much detail in your superstructure with the 'blooming out' of the white highlights. I know this happens in real life, but in order to convey the design shape to the client it may be better to reduce this effect a little. Maybe by a combination of material tweaks and a bit of photoshop work.
6) Are you using global illumination or faking it with multiple lights? I'd always go for GI even though render times will be greater.
Overall I'd say you were 80% there, just a bit of tweaking and you'll have a pretty impressive portfolio piece.
By the way, what software are you using for modelling/rendering?