Garmon 305 and arm band

I just ordered the 305 - took me a while to decide between that and the 310xt, just couldn't justify the $250 extra for the waterproofing, extra battery life and fibrating alarm feature.  But I would like to wear the transmitter in the water, some have said it is ok under a wetsuit but I'd rather use my polar transmitter for HR as it is totally water proof and I can then also have my polar HRM on to get that info while swimming.  I'll go to slowtwitch.com and ask because I am very interested.

1 - Not sure about the Polar transmitter, my gut leans me towards no.
2 - Do not worry about it being 'clunky' I noticed it for about the first 2 miles I ran with it, then you just get used to it.  I would highly suggest getting the quick release, the strap is much more comfortable.

My wife even tried it a couple of times and decided to get one at Bestbuy since they were on sale this week and she has tiny wrists.

I do notice it and it bugs the heck out of me.
It doesn't fit the way I'd like it to and it wants to slide around on my wrist.  The only way I can get it to stop doing that is to tighten it so tightly that it's uncomfortable.
I have even tried changing to a different strap.  Same deal.  I think it's just the weird shape that it has.  At least as it fits my wrist.

Scott

No go on the polar/garmin compatibility. They don't work with each other unfortunately.

Even if you wear a polar which is "fully waterproof" doesn't necessarily mean it will read correctly underwater.

Read at polar

x2 on buying the bike mount/wrist strap.

I love my 305 and don't notice it while running.  I bought the bike mount kit on Amazon for like $25 and the 305 snaps off the wrist and onto the bike instantly.  The rubber strap that came with the 305 bugged the hell out of me b/c it just didn't fit my wrist and moved around while I was running.  The velcro strap that came with the bike mount fixed that problem nicely.

As for wearing it on the arm, you could try using the velcro strap, but you would have to be really skinny.  I'm not real muscular and I tried to fit my strap around my bicep and it doesn't even come close.  I just don't think it's plausible.  You also wouldn't be able to read it comfortably.

I'm betting that you would be surprised about how little you notice the watch once you have it on.  I remember thinking the same as you when I saw people in my running group wearing the watch, but once I actually had my own, I was surprised to find that it's not as big as it looks.

Oh, and as for swimming with the 305 - I have done this and it actually works really well:

http://dcrainmaker.blogspot.com/2007/09/how-to-swim-with-your-garmin-forerunner.html 

Good luck, whatever you decide! 

I have also found it much easier to wear the watch on the underside of my wrist and not on top, both for comfort and ease of reading.

I second the above method for swimming it works wonders!