Great water shirt
The fabric is very comfortable and durable, and this shirt is a good fit: I am a 34C/D, and I purchased a Large. This shirt is good for kayaking or surfing.
Great as a modest swim suit
I bought this to swim at our gym's pool, and I love it! I don't like feeling exposed in public, and this swim shirt/rashguard has got me swimming again. I'm 5'7", 180 lbs, 38B bra size, and typically wear a size 14 in clothing - the XL fit great. I also tried on the L, which fit, but was a little snug - guess it just depends what feels comfortable to you and if you're wearing this over or under something else. I wear my rashguard with the Patagonia Meridian board shorts (size 14) that I also got from this site over a bikini swim suit. The neck is a little tight, but bearable, especially in the larger size. Any tighter and I probably would have returned it for something else. I have great mobility in this. I can move my arms all around and there's no restriction of movement from the fabric. The shirt goes down to about my hip bone and stays in place and doesn't ride up my stomach when I swim or stretch. I do feel a bit of drag when I swim in this, but I expected that since I'm now covered in fabric - and since I'm just doing it for the exercise, I don't mind. The colors are really bright - which I'm not crazy about, but again that could be a plus for some if visibility is a safety concern. It's comfortable, keeps me warm in the water and cool out of the water. If you're drip-drying in the sun, it dries relatively quickly but not immediately - the fabric is somewhat thick, and will hold a little water for a while. If you're trying to dry off quickly with a towel after swimming to, say, get back into your car - you might consider bringing an extra towel or change of clothes - but maybe I'm just impatient :) I burn easily, so I like having the extra coverage without having to apply sunscreen to my back. It's comfortable, very smooth - the seams aren't annoying... Construction seems really solid. I've machine washed mine several times and it seems to hold up well (I always let it dry on its own though). This is the only rashguard I've tried, which I chose based on reviews, but I like it so much I haven't tried another one yet. If you're looking for a rashguard / swim shirt for whatever water activity you're into, I would definitely give this one a try.
This is the first rashguard I have purchased. I bought the XL. I am a 40 D bra size. The chest fit snug. The rest fit good. It depends on how tight is comfortable for you. I probably could have gotten away with a L but am happy with a little extra room. The material is great, heavy duty and will last a long time. The colors are great to choose from. Also take into account the rest of your build.