Instructions
Capture the fan geysers on Eddie's side of the bridge. The geysers provide you with troops, so it's imperative you bring them under your control immediately. Including the geyser you start with, there are five.
Build a force to hold your side of the bridge. Make sure that your units only total 34 in number, rather than the full 40.
Begin to upgrade your buildings and troops, focusing on your main stage. You will need a level four stage before you can press the attack on Drowned Ophelia, as her tower defenses will shred any troops you send over before that. With 34 troops at the bridge, you should be able to hold back her attacks long enough to upgrade everything to its highest level.
Build a Rock Crusher once you've unlocked it by upgrading your stage to level four.
Use the double team command to take control of the Rock Crusher.
Drive the Rock Crusher over the bridge until you can use it to blast the towers on Drowned Ophelia's side of the bridge. While the Rock Crusher can fire from a greater range than her towers, you will be attacked by her troops, but they shouldn't pose much of a threat.
Order your army to cross the bridge once the towers have been brought down.
Order your army to attack the giant tree that will attack you once you advance over the bridge. Your army won't do much damage to it. However, your army will distract it long enough for you to use the Rock Crusher's weapons to destroy it.
Advance to Drowned Ophelia's stage and destroy it. At this point, she'll only have a few minor troops who will pose no threat to you and the remains of your army.