Lost Keys Lake is the second location in Plants vs. Zombies 3. There are currently three plants to be unlocked, Squash, Lily Pad and Tangle Kelp, and six new zombies to encounter, Ducky Tube Zombie and all gender and armored variants thereof.
The area mostly takes place in a forest full of pine trees next to the river. A waterfall can be seen on top of the lawn. There are four large footsteps pasted on the mud leaving small water puddles behind. The player now must guard a small tent in the middle of the forest from a horde of zombies.
The main gimmick of this area is water. The water in this area cannot be directly planted on, barring aquatic plants, similarly to Pool and Fog from Plants vs. Zombies and Big Wave Beach from Plants vs. Zombies 2.
But unlike those aforementioned areas, the water areas has a special side effect where non-aquatic zombies will move slower upon swimming in the water, while aquatic zombies move faster when swimming in water. There is also a chance for there to be Water Surges, where all aquatic plants in the water will be shifted one tile in the direction the water is flowing. Plants that are at the edge of the field during a Water Surge will be lost.
In each level, the water areas might have different shapes and form, similar to pathways the in Qin Shi Huang Mausoleum from Plants vs. Zombies Online, although this does not affect any aquatic zombies moving up or bottom.