Plant two rows of Sunflowers and Potato Mines for sun. Plant Potato Mines to fend off the first two to three zombies. Then, start to plant Repeaters or Snow Peas on land and Wall-nuts evenly on each pool lane two columns in front of two columns of Snow Peas or Repeaters. Then, place Spikeweeds on every other spot on land.
Depending on your preference of plants, you may find the Repeater redundant when you get the Spikeweed. If so, plant a column of Snow Peas (two on land) and on the rest plant Spikeweeds to maximize damage.