I've always loved the idea of elemental druids but I'd go a bit further than changing the spell list. Something like:

Add Knowledge (the Planes) as a class skill.

Aquan as a bonus language instead of sylvan.

In addition to the normal list the animal companion may be a water elemental (as the elemental companion from complete mage) or a aquatic animal companion (as the aquatic animal companion from stormwrack).

Woodland Stride + Trackless Step replaced by something like walking on water (possibly a limited time per day) or a swim speed.

Resist Nature's Lure and Venom Immunity should also be replaced by something.

Elemental Wild Shape can be used to wild shape into any elemental (small, medium or large) with the aquatic, cold and/or water subtype but not other elementals. The new formís Hit Dice canít exceed the characterís druid level of course.

Wild Empathy should be changed to something like:
A druid can improve the attitude of a creature with the aquatic, cold and/or water subtype. This ability functions just like a Diplomacy check made to improve the attitude of a person. The druid rolls 1d20 and adds her druid level and her Charisma modifier to determine the wild empathy check result.

The creature must have a con score. For every point of intelligence the creature has above 2 take a -2 penalty on the check.

To use wild empathy, the druid and the creature must be able to study each other, which means that they must be within 30 feet of one another under normal conditions. Generally, influencing a creature in this way takes 1 minute but, as with influencing people, it might take more or less time.