This level is relatively easy, for there are only few types of zombies in this level. The Seagull Zombie can fly over the gaps where no planks are present, and is faster than a normal zombie. Unlike most flying zombies, this one still has the ability to eat plants. Using a defensive plant like Wall-nut can help stall this zombie. In addition, the Kernel-pult given to the player before this level can instantly kill it if butter is thrown at it.
The small number next to the zombie icon means that zombie will always appear in that lane, with 1 being the topmost lane and 5 being the bottommost one.
Plant two columns of Sunflowers, however, leave at least two (or even more if you wish) tiles in the second column blank to save them for other plants that you have to plant in the future.
Use either Peashooters, Kernel-pults or even Bloomerang when dealing with Pirate Zombies and Conehead Pirates. Make sure you have enough of the aforementioned plants in case you are dealing with these zombies in large numbers.
Use Bonk Choys in dealing with Seagull Zombies since they often bypass other plants, thus making them a pain to deal with. Bonk Choys are useful in knocking out Seagull Zombies in a matter of seconds, even before the Seagull Zombies will try to consume them.
Lastly, use Iceberg Lettuces wisely and carefully. In the case of big waves of zombies, you can use Plant Food on them, which will allow the Iceberg Lettuces to freeze the zombies in place for several seconds while you take the time to strengthen your defense.