Heat 600 ml of water until hot, then pour it over the dried hibiscus flowers.

Steep the hibiscus infusion for about 10 minutes until deeply red.

Strain out the hibiscus flowers and let the infusion cool completely.

Cut the watermelon slices into chunks, removing any seeds if needed.

Blend the watermelon chunks with the lime juice, 300 ml water, agave syrup, and cooled hibiscus infusion until smooth.

Transfer the lemonade to a pitcher and chill until very cold.

Pour the chilled watermelon hibiscus lemonade into four serving glasses.