Photographing a beach party

Hi,
I am supposed to photograph my friend's beach party in two weeks. I am planning on using a Ricoh GR1v (28mm) for this. I've had good results before with this camera photographing events. The only problem I have with this camera is that it only goes to 1/500th sec shutter speed. I assume midday on the beach with sand reflecting sunlight this will really limit what films I can use. 30.5 mm filters are hard to find. Any suggestions on what film I should use for this?

Use negative film, over expose by 1.5 or 2 stops when sand etc is in the picture. Same as for snow.

Maybe Kodak Gold 200 at EI100 or EI50? Or Ektar at EI100 or EI50?
I'd like to use slide film for popping color. Nuff, your shot here on slide look fine and that is a similar lighting condition I guess.

Yes, I did. But I used a spot meter and I had to check and recheck to double and triple make sure the exposure was correct Not to mention it was very windy with -25C wind chill that day.
And on top of that you will need to learn basics of zone system
I also took one photo which ended up being under exposed.

Here's another one which I took about 30min later and I didn't get it quite right, because of the fast changing conditions. I wish I gave it a bit more exposure...
https://www.flickr.com/photos/jareksm/14168947186/

If you want more more pop, shoot Ektar, it has enough pop and latitude to be more forgiving of mistakes. Personally I would also take a roll of Portra 160 and shoot it at 80. Since you are taking photos of people and I assume women, I think they will appreciate if their skin looks good instead of like a bunch of smashed crabs

I don't like the red skin Ektar gives. I'm not sure if your audience will be Japanese women, but if it is, I'm not sure they will like it either. They use a lot of skin whitening products to get their skin as white as possible, it's also why Fuji Pro 400 (PN400N and to lesser extent 400H) have less red in it. It's your choice after all, but just for that reason I would use Fuji 160NS over Portra 160, less red/yellow.

Beach shots are a problem on sunny days. I know because I've been shooting them for 3 years now. The sun will reflect off the sand causing a high reading, the water will be another value, the sky will be whatever it is at that particular time of day, and people will be another value, especially if the sun is above you or at an angle. Depending on the sun's location on your shooting day, all this may be out of the exposure range of most films, so you'll have to prioritize what the important elements are, and be ever watchful of where the sun is in your shots.

On bright days its very easy to get great exposures of the sand, water and sky, but get shadowed people. An overcast day will be your friend. Flying bird shots are tough too, as their undersides are often in shadow, so the sky can get blown out and grainy. You're fortunate in that you have two weeks, so I would shoot some test rolls at different times of day and get a feel for how your camera is handling things.

Adapters are available to put filters and hoods on your camera, but since your camera does not have TTL metering (I think), and only allows 2 stops of exposure adjustment, trial shots would be highly suggested. I use Tri-X film w/ a yellow filter and rate it at 100 ISO. More important than your film selection is your developer. I wouldn't use Rodinal! TD-16, D76 and Acufine have worked great for me. Or, make your life simpler and use C41 B&W, and you won't have to worry about grain.

Beach party? I guess the primary subjects are people. I would use Portra 160 and incident meter.

Fantastic idea. Just searched for beach and portra 160 on flickr and really like what I see.

Portra 160 should be great, both for people and backgrounds.

As you have two weeks left, you could try sourcing a C-Pol filter off the internet. It will help you a lot with the sea-sand-sky problem.