I am thinking about building a spirit whisperer wizard with the crashing waves hex (see below), the rime spell feat using the river whip spell.
As I see it any target damaged by the whip would be entangled and would have to make a a fort save or be dropped prone. Is that right?
Crashing Waves:
The force of a waves shaman's water spells can bring even the mightiest of foes to the ground. When the shaman casts a spell with the water descriptor, she does so at 1 caster level higher. If that spell deals damage, the target must succeed at a Fortitude saving throw or be knocked prone. At 8th level, the shaman casts water spells at 2 caster levels higher. At 16th level, her ability to knock creatures prone extends to any spell that deals damage.
I must be missing the reason that Rime Spell applies to this. It only affects cold spells and River Whip is not a cold spell.
Certainly the Crashing Waves hex applies to to River Whip, and it will knock him prone but it won't entangle the victim unless you find a way to apply Rime Spell to River Whip (either by adding the cold descriptor to the spell or by making Rime Spell affect spells without a cold descriptor).