I've also heard both ways...
(1) that a little gap between them (not WIDE open) doesn't really let the water through and gives you a larger pulling surface
(2) that while the little gap can help some people (in particular women) seem to go faster with them tighter (although not so tight you are stressing and wasting energy holding them there).

Hopefully one of the swim experts (geo?) chimes in :) I'll be interested to know.

here is what i have been told (and believe/practice): while you are in the power part of your stroke your hands should be relaxed. this allows them to slightly change shape to accommodate any fluctuation's in the water that they are pulling through. this does not mean that you should have gapping spaces between your fingers. you should aim to keep them as close as possible, but keep them relaxed so that they are not clenched closed (if that makes any sense). personally, i rarely think about it when i am training, and my mind is focusing on other things while i am racing.

best of luck!

I've always done it with my fingers closed. I am not a strong swimmer so my input might not be the best. Having my fingers closed has always helped me hold my form alot better. When my fingers get open, I tend to "slap" the water more than swim.

CGroth, RV and especially Geo are 100% correct. Natural hand pull through the water. If you cup the hand it stiffens the forearm and allows for more power generation. My 2 cents

The hand is not to be in a complete cup. Slight cupping sounds Ok.

You can see how I hold my hand when I'm swiming in the pool on my home page. It is at a relaxed pace the hands are slightly cupped the fingers slightly open. You can find this hand position by standing straight up and let the arms hang loosely. The hands go to the natural position. See me puddling along on swimdownhill.com home page.

It's a little different for everyone. Here's a couple general guidlines:
1. If your hand or forearms cramps - you're doing it wrong
2. If you're exerting energy to create this hand formation - you're doing it wrong.
3. You want to feel the water
4. fingertips are to the bottom of the pool/lake at all times

I was taught to keep the hand relaxed, slightly cupped, fingers slightly apart. This gives greater surface area due to the webbing effect of water flow between the knuckles. If you spread the fingers too far apart, you lose that effect and spill water through the fingers. Too tightly cupped and you lose the extra surface area and also are tensing your hand too much.

That being said, I have a really strange hand position. I bend the top knuckles of my fingers first at the beginning of the catch without bending the bottom knuckles. I always thought this was very strange, but read on a coaching website once that many competitive swimmers can do this with their knuckles. So maybe it is advantageous after all in some way.

I interpreted it differently. I thought he was saying that the hand wasn't flat on top of the water at the beginning of the stroke so that the hand is already catching water even in the fully-extended part of the stroke.

I know this isn't the best picture, but you can see that the hand is cocked and ready to pull already, even the though the stroke hasn't even started yet.

in geos post, that picture is what i imagine a dropped elbow to be.. am i all screwed up? i always try to keep my elbow closer to the surface than that and now i think im doing something wrong

Here is exactly what I am talking about http://www.h2oustonswims.org/articles/dreaded_dropped_elbow.html

same here.. ive been bending my elbow way too much and keeping my hand too close to my body thinking i was right.. thank u