Undertow

Difficulty: Easy-medium

Undertow is an achievement in Plants vs. Zombies 2: It's About Time. It requires the player to kill 10 zombies with Tangle Kelps which is worth 10 points for iOS devices.

Strategies
Play Big Wave Beach - Day 5 because you can get a lot of Tangle Kelps in this level. But, try to focus on strong zombies too.