need help fast with a blister

wrap your feet in coban, it's the stretchy stuff that holds the gauze on when you give blood.  You can get it at Target.  Just wrap one or two layers over the area where you usually get blisters and it's GUARANTEED to keep you blister free.  Not sure how well it'd stay on in the swim, but I use it on runs all the time.

Good luck.

 That's not where you "kester" is!! 

Moleskin bandages. You local drugstore will have them. They're self-adhesive. You could stick 'em on in T1.

x2 on the Moleskin.

If your heels are blister-free, and your only concern is the run, clean and dry (an alcohol wipe can really help) your heels in T2 and slap a piece of duct tape right over the skin.  Moleskin works, but comes loose easily (at least for me) and ends up where 1) it doesn't help and 2) you don't want it.  Be generous with the tape.  It should pretty much cover your heel and not be wrinkled. 

The duct tape will prevent friction on the skin without the bulk of a bandaid or moleskin. 

If you've got sores from previous blisters, dab some triple-antibiotic ointment on the wound before applying the duct tape (it'll keep the tape from sticking to the scab, and you're putting non-sterile stuff on the wound). 

if you already have a blister, bursamed will keep it from rubbing and sticks much better than the bandaid brand stuff.

I know REI carries it.

http://www.sammedical.com/bursamed.html

if you do not have a blister, but it is a hot spot, then blistoban is designed for this:

http://www.sammedical.com/blistoban.html 

I used to get bad blisters on the backs of my heels while I was hiking (I've never had the problem running), since I also have pretty bony, skinny heels. Two things I've done to prevent them:

Get a pair of Wright socks from your local running store. They are double layered socks that are supposed to help to prevent blisters, because the sock rubs against itself. I got a blister once while running in a new pair of shoes, bought a pair of these, and went out in my old shoes with them and the blister didn't get any worse.

Try putting Bodyglide all over anywhere on your foot where you normally get blisters. This helps me a lot with blister prevention.