Fuel is available in town but you will have to carry gas cans back and forth from the dock. The situation in Mariscos, on the south shore is the same but there are young boys with pushcarts who, for a tip, will fetch the fuel for you as it's several hundred yards from the pier to the gas station. Five Quetzales per can is a typical tip. In the center of Fronteras is a typical Guatemalan open-air market where its possible to buy everything from fresh vegetables, fruit and meat to soap, pots, pans, shoes, rope and kerosene. The many sellers compete with each other which keeps the prices low.
Prices are always negotiable.
On weekends, an additional, larger market is set up under the bridge on the north bank, There are several places which are set up for professional provisioning of boats where large quantities of professionally packed meats and other foods can be ordered. They represent the same companies that provision the freighters that sail from the ports of Puerto Barrios and Santo Tomas. There are several marinas in picturesque settings along the Rio Dulce. Most also offer hot showers, cabanas and a restaurant. Some offer a laundry service.