Here's a spell I missed from Oblivion. I mean, sure you could find the potion, and there's ONE undisenchantable pair of boots that has the enchantment, but in case you don't want to take the time to look for the potions, or if you don't want to lug around a heavy pair of boots, here's the spell. Just buy the tome from anyone that sells Adept level Alteration spell tomes. The duration and spell cost is basically identical to the waterbreathing spell.

Also, Talvas Fathryon in Tel Mithryn sells the tome as well.

UPDATE: Now I've included two spell tomes for people like me who don't like to fast travel, don't want to put in the expense of a horse that could get killed, and just want to hurry up and GET THERE!!! (Or get away if you're in over your head.) The first is Fleet of Foot, which allows you to run 50% faster. The second is Run Like The Wind which makes you run 100% faster. Both spells last for two minutes... three minutes if you have the Stability perk. You can either buy the tomes from anyone selling Apprentice and Adept level Alteration spells, or if you're in the Thieves Guild, you'll find the tomes in a couple of Thieves Guild locations.

NEW UPDATE: I changed the name of "Run Like the Wind" to something a bit more appropriate, "Kiss of Kynareth." If you want to know where I got the idea for that name, read the game book Rislav the Righteous. I also added scrolls of the running spells.

Enjoy.