Add the blueberries, cranberries and water to a saucepan and bring to a simmer over medium heat, stirring occasionally. This will take about 5 - 7 minutes.
Simmer for 5 minutes, stirring often. As the berries begin to soften, use a wooden spoon or fork to mash about half of them.
Stir in the chia seeds, maple syrup, lemon juice and salt and continue to simmer, while stirring, until the mixture begins to thicken, about 3 - 4 more minutes.
Remove from heat. The Jam will continue to thicken as it cools.