After a bit more research, I can see a reason to get rid of the swim speed, since waterbending was learned by watching the moon and tides, rather than fish:
Originally Posted by Wikipedia
The people of the Water Tribe first learned Waterbending by observing how the moon pushed and pulled the tides of the ocean. They then learned how to do it themselves.. According to the episode "The Waterbending Scroll", the word waterbending is written in Chinese as 截水神功, which is best translated as "The Divine Ability to Halt Water".
(???? = characters that my computer can't see. anyone know where I can get a plug-in to read Chinese characters?)
Still, I think the ski/water walk thing should remain a seed. It still seems like something that would need to be learned. Not sure why, just kind of a gut thing after watching entirely too much of the show for the past couple days.