Reducing your movement speed penalty will also reduce the cost for swimming.

Originally posted by Cap'n Bells:

Yeah i meant an additional benefit to swim skill. being "treading water" so you can stay "undrowned" and rest as the swim skill grows so does your ability to rest.. and even eventually to be able to fight whilst floating ... even get to shore if nothing in ocean eats you :-)

Sure, games just tend to cut the less engaging parts out. You can also get that effect with stamina mead. :p

The skill could scale better, certainly, or it could be trained faster.