Snorkeling in Fiji - DLSR + housing or point-and-shoot?

Shoot in RAW format and take a piece of white plastic with you. Take a shot during each dive of the white at various depths so you can correct the white balance later ;-)

I'm a hobbyist underwater photographer. (Some of my photos are on my flickr page, most are on Facebook). I always use a P & S, because I like to travel light. At the moment I have a Sony RX100 mII with Ikelite housing. Before that I had various Canon G models. All of my cameras after the first one have had the ability to shoot RAW and to do manual white balance. For me these are the two most important features, as light behaves differently under water than above water. See http://news.scubafish.com/latest-news/a-beginners-guide-to-underwater-white-balance/. I usually white balance off of my hand or sand, and shooting RAW allows for further colour correcting in software. If you are only going to snorkel, in 5 - 10m of water, a P & S will probably be good enough. Most P & S cameras today have an underwater setting which adjusts the white balance for shallow depths. If you are diving/going deeper you will want to white balance each shot. As you are a "fairly keen and knowledgeable hobbyist photographer" I would say go for the cheapo body and case for the m4/3 lense. This will give you better quality images and MORE CONTROL over your photos. Try and get a body that allows you to white balance with one button push. This was possible on my previous Canons, but I have to go into the menu on my Sony, entailing many button pushes. Pain in the ass! A tip I picked up while on my last trip to Palau; it's better to underexpose underwater shots and correct in software. It's very easy to overexpose under water, and overexposed shots can't be easily corrected. Err on the side of caution.

I live in Hawaii and do lots of scuba, freediving, and photography. I would recommend a GoPro on some kind of buoyant handle if you are snorkeling. Bigger DSLR housings work best when you have a stable platform and plenty of time to shoot, so I can't imagine snorkeling or freediving with one. Smaller point-and-shoot setups work rather well, but the GoPro is far more streamlined and easy to use underwater. Especially when you are kicking down to 5-8m for a close shot on a single breath of air. The LCD backpack for the GoPro makes composing video or still bursts much easier, but chews battery. If you're not into the GoPro lineup, a Canon point-and-shoot in a decent enclosure is my next best recommendation. Regarding Mac-Expert's comment on post filtering: get a red filter for your setup (GoPro makes one, or get fancy with a Backscatter Flip). At depth, the water gets so blue that you won't be able to pull much color out in post, whereas a properly filtered capture is a lot more flexible. I have not yet needed a white balance card, but ymmv. Underwater photo (when snorkeling) can be tricky... simple is a good thing. If you do get certified (do it!) and plan to spend more time diving, then go nuts. Oh, and enjoy Fiji!

I'd say it depends to some extent on how much you think you might get into underwater photography in the future, as well as how much you already use your m43 camera. The fact that you only have a single kit lens (assumption) for your m43, and that you'd be using an older body (GF3) means that you're not really heavily invested in the format. If you see yourself doing more underwater photography in the future, and/or you already use your m43 kit heavily, and/or you plan to use your m43 kit heavily in the future, and/or you're interested in adding to and upgrading your m43 kit, I'd probably go with the housing for an m43 camera. I say all this as a fan of the m43 system. Metafilter helped me choose an Olympus OMD E-M5 back when I was shopping for a new camera almost 3 years ago. I've been very happy with the choice, and now own a small stable of m43 gear, including 7 lenses, an Olympus E-M5 and a Panasonic GM5 (super, tiny camera, but a little pricey - the GM1 is a tad smaller and somewhat cheaper but doesn't have the GM5's built-in EVF, which isn't a deal-breaker for some), and I'm planning to trade my E-M5 in for the just-released E-M5 Mk II ASAP. In short, if you're into photography, m43 is a fun, compact, quality system with a range of different body styles and sizes, a ton of high quality native lenses and all kinds of accessories from a number of manufacturers. If you're interested in sticking to that format and growing your collection of gear, it would probably make sense to go the m43 route for this trip. One other note - I would suggest doing some thorough searching for refurbished bodies. You may find that you can get a refurb (with warranty) GF5 or GF6 for not a whole lot more than a new GF3 - much better image quality at a very small price premium.

I'm also a fairly nerdy amateur and I bought Mrs. Advicepig a predecessor to the Panasonic you mention. I swam with my nicer camera in a housing. I had no idea how much I fought with that housing. Using her underwater camera I was able to frame and shoot so much faster. We shot somewhere around a stop or a stop and a half underexposed and did very little cleanup afterwards. It's got a solid underwater mode for snorkeling, but the red filter mentioned above sounds super appealing. Next time we get a chance to go, I'll be buying another underwater camera.

The fact that you only have a single kit lens (assumption) for your m43, and that you'd be using an older body (GF3) means that you're not really heavily invested in the format. Hey there, you have, I'm afraid totally misinterpreted me: I would be buying the gf3, and using the kit lens I hardly use now because of all my other lenses. I am, as mentioned, experienced, and knowledgeable, on land - it's how it all plays out in the water I'm not certain of!

Advicepig, so you found the quality of the point and shoot okay?

Pros for P and S: Small and easy to handle; not lugging a trillion pieces around with me and can shoot in one hand no worries. F.2 lens on Pentax good for low light, in fact better than dslr with kit. And, you're snorkling...Why burden yourself with all that kit? You'll find yourself taking more pix with the smaller more portable camera. There's no need to remove the camera from a case for above water shooting etc.

I found the quality as good as I could reasonably expect. We made a wall calendar with some of those shots in it and they look great even printed at 12 x 12 in. I don't tend to print any larger than that, so I can't tell you how they would look in something huge.