Supernauts Mission Guide: San Francisco - Mission 3, Walk On Water

Objective: Rescue 1 Citizen
Reward: 1 Coin, 3000SP

It's time to rescue Debbie Cooper, so grab the nearby Strength Mushroom, and pick up a trash canister to fill the gap in the land, forming a makeshift bridge.

Now pick up another trash can and make part one of another bridge to the next island (acquiring the coin at the same time) and then grab another to complete this bridge.

Next, pick up the Zapper on this island so you can zap Timber, and the pink Strength Mushroom so you can lift the big blue trash canister on the previous island.

Use the canister to create part of yet another bridge towards a nearby door of Timber, and finish the bridge with other trash canisters. Once you're across, zap the Timber, freeing Ms. Cooper.

Once she's on the nearest island, build a final bridge, going towards the Rocket, and add a couple of blocks of Timber to reach the ledge.