Big Wave Beach - Day 18 is the eighteenth level of Big Wave Beach in Plants vs. Zombies 2. It is a Special Delivery level. It allows player to use the Guacodile before obtaining it. The tideline in this level is located behind the first column, which means that the tide will rise, and water will cover the entire lawn at one point during the level. After completing this level, the player receives a money bag.
Only ten Guacodiles are given, and there are a lot of zombies on the lawn when the first wave appears.
Normally, you can beat the level using only lawn mowers if you do it properly, although it is extremely difficult. The key is to try to save as many as possible for the final wave, so they either kill the Deep Sea Gargantuar or most zombies in other lanes, allowing you to focus all your plants on the Deep Sea Gargantuar. However, it is possible to beat this level without the lawn mowers, only using the Plant Food provided.
Plant three Guacodiles on the first three Lily Pads. Plant others in the back column, even if there's still water there, as the tide lowers rather quickly and never rises back up there again.
Plant as many Guacodiles as you can to the left. Try to keep zombies from setting off the ones at the back column, but it will happen at some point.
When the first Octo Zombie appears, use Plant Food on a Guacodile in that lane and plant a new Guacodile right in front of it to kill it easily. Try to use Tangle Kelp on other Octo Zombies as soon as they appear. You may also want to shovel plants that are being attack by octopi to keep the space from being occupied by an octopus.
When seeing Deep Sea Gargantuars and they are close to Guacodiles, feed Plant Food on them to push the zombies and deal enough damage.
Try to save Magnet-shrooms for the Pompadour or Bikini Bucketheads. You can also use Plant Food on them to help clear out undefended lanes, but make sure there are some Buckethead Zombies on screen, so it will actually have an effect.
Try to plant the tenth Guacodile on the same tile as the zombies and keep planting Lily Pads and Magnet-shrooms on the lawn. You can usually get Guacodile again on the conveyor-belt and damage zombies at the same time.