Start by washing the tangerines under running water, ensuring they're clean and fresh. Slice them into thin rounds, and discard any seeds.

In a large pot, mix your sliced tangerines with sugar, fresh lemon juice, and water. Stir gently to combine.

Place the pot on the stove over medium-high heat. Bring the mixture to a gentle boil while stirring occasionally.

Once boiling, lower the heat to a simmer. Let it cook uncovered for about 45 minutes, stirring occasionally until thickened.

Drop a spoonful of the mixture onto a cold plate to test for doneness. If it sets up nicely after cooling, it's ready.

Carefully pour the hot marmalade into sterilized jars. Seal them tightly and let cool before refrigerating.