The main trouble in this level are the Seagull Zombies, because of their speed and their immunity to Spikeweeds' attack. A Wall-nut should be used to stop this zombie in case there are only one Threepeater able to attack it. The player has to think of a way to deal with a relatively high number of Pirate Zombie and Conehead Pirates as well.
Strategies
As always, the player should break the plant vases first to get Threepeaters, which are crucial in this level.
Although the Spikeweeds can easily be bypassed by Seagull Zombies, they are still needed to deal with Pirate Zombie and Conehead Pirates. Try planting one of them on each lane.
If there are too many zombies, the player can use Plant Food on either Spikeweed or Threepeater, depending on the situation.