@ Tatsua,
That actually sounds hilarious.
Lose every single fight because everyone is a water user.
@Yog,
Also, the mist village, where the ninja are trained, is on an Island. That's the point he's making, Yog. I'm sure you've noticed in the series the references to aquatic animals and the mist village. Kisame used sharks, not bears. There is a theme revolving around the Mist village. Though, again, I don't think it is a big deal in regards to summoned creatures, the point is water. You most likely wouldn't see a desert tortoise or a scorpion summoned by a Mist ninja. It would be weird. Also, clans are typically in a respective village and have a respective element related to that village. i.e. Uchiha and land of fire.
There is a theme in Naruto and the villages.