Cook the spinach for a minute or two, until just wilted. Squeeze dry and set aside.
Add avocado, mayo, lime juice, maple syrup, salt and pepper to the bowl of a small food processor and process until smooth and creamy.
Add spinach, water chestnuts and sun dried tomatoes and process on pulse until well combined.
Chill for a few hours before serving to allow for flavors to fully develop (not absolutely necessary but preferable); to avoid discoloration, cover with plastic film placed directly on top of the dip (in direct contact with the dip)
This will keep in the fridge for a few days, so long as you keep it well covered and avoid contact with air.