It seems you've seen moon snail's defense, right? Well this is one of mine to survive dead man's booty level 15.
Here are the plants are most needed.
- twin sunflower (obviously)
- melon pult
- iceberg lettuce
- spring bean ( for early on).
- kernel pult
- winter melon
If you have 8, cherry bomb or potato mine is useful. Chili bean is useless.
Get sun extremely fast. You have 3 or 4 flags. I got 4 plant food since level 1. Save it until you need it the most. Kernel pult , iceberg lettuce, spring bean and spikerocks are needed for early winter and melon pults.
To look at the most powerful defense, look at my profile pic to get a better view.