Yes. Find a cute girl to walk on the beach with you. You'll look great!

Sorry, couldn't resist. :)

Get a spray tan. Every guy looks more buff when he's tan.

IMHO: Attractiveness comes from within. As a guy, the simple act of fretting about your physical appearance is inherently less attractive than moving on with your life and accepting that one week is not enough time to produce any substantial lifestyle change that makes you look better.

I'll be in your shoes in a few short weeks. I'd do strict low carb/sodium for at least a week for sure. Mostly protein, and some greens and that's about it. No alcohol or sugar at all. All I'm eating the week or two before I leave is eggs, meat, and a few veggies. Have fun!

The really quick fix: http://www.hulu.com/watch/195627/abc-nightline-abs-in-a-can

The only thing you can really do is lose body fat. Playing with sodium/water retention levels is difficult and could only be maintained for a day, if that.

Your muscles will likely look smaller if you cut carbs heavily due to lower glycogen content. Probably not what you want.

A PSMF is your best bet. It will suck (I've tried it) but you can drop a few pounds of fat in a week. You should find a better resource that this wikipedia article on how to do it safely (e.g. Lyle McDonald's rapid fat loss handbook) but it's a good summary.

http://en.wikipedia.org/wiki/Protein_Sparing_Modified_Fast

find a deserted one............

This is going to sound cheesy, but if a guy slaps on a smile and looks straight into my eyes, I barely notice his body. It forces me to look at his face. If I'm looking elsewhere, I'm simply being rude.

Confidence really does come from within.

If you are up for a strange experiment, try the judicious use of red wine. I have noticed red wine is an incredible diuretic. In fact, you need to be somewhat careful with this experiment, since we are talking about purposefully being dehydrated on a beach. Vanity could be deadly. I don't think dropping sodium is a good idea. Traditional 'shredding' techniques come from wrestlers, who are trying to make a weight. You don't need to make a weight, you need to make a good impression. How about putting that water into your muscle cells where they will contribute to you looking muscular? Creatine puts the water into your muscle cells.

You will need to drink water and keep your electrolytes balanced if you do any of these things. That's why lowering sodium is such a bad idea. You'll be flushing out so much sodium you will probably need more than you usually take in, especially in a hot environment.

Whatever you do, be just a wee bit more in control than the rest of the crowd.

Go shopping. Buy some nice t-shirts and well-fitting swimsuits. A tan wouldn't hurt, but don't over-do it. Get a haircut. Shave. If you can stand it, go get a facial for nice glowing skin. Get your teeth whitened. Get a pedicure (have you seen your toes since October? -- all the ladies are about to).

I second the tan suggestion. Unattractive abstractly, I know, but still.

A well fitting swimsuit that shows off your ass! Like a Brazilian sunga, the traditional speedo or a vintage pair of short swim trunks!

Leave the baggy jams and NBA-style shorts at home.

Your best strategy for losing water (if you don't want to take illicit drugs) is Sodium loading.

Start lowing your sodium about 10-15 days out. Don't deplete your levels too quickly - this is to prevent too much aldosterone getting released (Aldosterone is a steriod that causes the body to retain fluid).

*Also increase your potassium a little more than normal, this helps.

15 Days Out - Begin sodium loading. Salt or season all meals and eat foods high in sodium.
10 Days Out - Reduce sodium to 4000 mg per day.
5 Days Out - Reduce sodium to 2000 mg per day.
2 Days Out - Reduce sodium to 1500 mg.
1 Day Out - Reduce sodium to 1000 mg.

Drink 2-3 gallons of water the days leading up to the beach, then cut it by 30% a day before, then drink enough water to quench thirst the day... but nothing more. Don't forget, muscle tissue is mostly water, if you cut your water too much you will lose alot of fullness.

5 days before, increase you carb intake higher than normal (150g+) for 2 days, followed by 3 days none (0g).

On the day:

2 hours before the beach: Ingest a high carb/fat/sodium meal containing approximately 75-90 g of carbs, 20-30 g fat, and 2000 mg sodium. This meal will really help you to fill out.

(By sodium depleting for several days prior you will have increased your body's ability to store more sodium. Since your cells have been deprived of sodium for several days they will be more likely to retain sodium (and the water that goes along with it) intracellularly and store less of it subcutaneously. Couple this with the increase glycogen retention inside the cell and you will fill out.)

Hope this helps