Big Wave Beach - Day 21

Big Wave Beach - Day 21 is the 21st level of Big Wave Beach. It is a Special Delivery level. The tideline is located between the first and second column.

Difficulty

 * Surfer Zombies are the main threat in this level as they can destroy the Homing Thistles with their surfboards or by wiping out close to shore. Adding up their constant pacings, high-speed ability, and their durable surfboard will allow them to reach further through your defenses with ease
 * The number of Homing Thistles given is six, and they come in relatively slow on the conveyor belt. This makes the firepower provided in the level fairly underwhelming.

Strategies
Once you get the first Homing Thistle, place it in the 3rd row of the backmost column immediately. This will allow it's attack to access zombies both high and low faster, and help you prepare yourself for the first Surfer Zombie that will appear. All Homing Thistles should be placed at the backmost column for an ensured protection also while your Lily Pads should go to the third and fourth columns or on columns where the water is. Lily Pads will also serve as platforms for Iceberg Lettuces. If you managed to get at least three of Homing Thistles at the start of the level it will be easier to take care of the first Surfer Zombie.

After defeating the first three Surfer Zombies, a script triggers for the shoreline to go in the fifth column and will be followed by the arrival of two Surfer Zombies (their appearance will be regardless of column) also. Keep on placing more Homing Thistles to hasten killing Surfer Zombies. If you managed to get stuck in a tight situation, you may place an Iceberg Lettuce to stall one or feed it with Plant Food if there are many Surfer Zombies. After this set is gone, the first wave will be triggered.

You can either choose now to give a Iceberg Lettuce or Homing Thistle some Plant Food but it would be strongly advised to feed it to an Iceberg Lettuce in order to put the Snorkel Zombies to a complete halt as well. This provides you with ample time to think of your next strategy and also save your Lily Pads. Keep at least one Plant Food for a last resort option. Save the rest of Plant Foods halfway through the first wave so you can freeze zombie hordes with Iceberg Lettuces for the upcoming waves.

At the second wave, another script will be triggered, and shores will hit the third column, which allows all Surfer Zombies to compensate. At this time, you may use stored Plant Foods to destroy any placed surfboards since the level has started or freeze the horde once more. Place excess Lily Pads on the second & third columns so Surfer Zombies will have to impale the plants in second column so there will be nothing left to worry about for the final wave.

For the final wave, the final script triggers the shores to touch the second column and the last set of zombies will arrive. Use the same strategies with Plant Food. The threat level is minimal on the final wave.

Trivia

 * Besides Piñata Parties, this is the only Conveyor-Belt level which has three flags.
 * Day 21 is the only Big Wave Beach level where Pompadour Zombie and Bikini Zombie variants do not appear.