Bridge Builder is the eighth mission in WorldBuilder.
Use the Steamshovel to make a bridge to the goal by digging up the land tiles and filling in the water tiles. Keep an eye on how much energy your Steamshovel has left, because it uses up a ton of energy real fast.
An optimal strategy for reaching the goal, while also having enough energy to get to the bonus goal, is to dig up the land tile behind the Steamshovel and place it in front of where you want to move, using the land tiles as a "raft" of sorts. Repeat this until you reach the goal.
At this point, unless you used the optimal strategy mentioned above, the Steamshovel you drove to the original goal is most likely very low on energy. Make a new one using the stack of bricks near the bonus goal, and make a bridge around the rocks on the water.
The optimal strategy for reaching the bonus goal remains the same.