Go buy the Wetland Walkers blueprint

Once the player finishes talking to Rosie Martínez about the "special equipment" needed to access the marsh, she will tell the player to use the Blueprint Machine to be able to build the Wetland Walkers. The blueprint for the Wetland Walkers costs $100. Once it has been purchased, the job will be complete and the player will be immediately assigned the next task of building the Wetland Walkers.