As I don't know much about his stats, I can only do a move
Floatzel's base attack is 20 higher than it's base special attack, so focus mainly on that. However, due to a small frame of avalible moves, you're a bit limited in choices.
I'd keep Ice Beam. Ice is such a good type when attacking. :)
You really don't need both waterfall (attack, 80) and surf (sp attack 95). It's redundant. Swap out waterfall for Crunch (attack 80).
You could swap double team for dig (attack, 80) or brick break (attack, power 75). Even though Brick Break is less powerful by five, your foe can't just switch out to a flying Pokemon and make it useless like they can with Dig.
Here's how the three types I sugested coordinate with your ice and water. (when attacking, super effective)
Ground: Fire, Electric, poison, rock, steel
Dark: Psychic, Ghost
Fight: Normal, Ice, Rock, Dark, Steel
Water: Fire, Ground, Rock
Ice: Grass, Ground, Flying, Dragon
(when attacking, not very effective)
Ground: Grass, Bug, Flying
Dark: Fight, Dark, Steel
Fight: Poison, Flying, Psychic, Bug, Ghost
Ice: Fire, Water, Ice, Steel
Water: Water, Grass, Dragon
One other advantage of Dig to concider is that Ground is super e. against electric, which is super e against you.
Overall, just bruch up waterfall and Double team and you're pretty good :)