Grate the zest from the orange and squeeze out the juice, then mix them together in a large bowl.
Stir in the flower water, if using. Add each fruit to the bowl as you prepare it.
Cut the top and bottom off the grapefruit, then stand it on a flat end and slice off the skin. Slice the grapefruit into rounds, then cut each round into two halves.
Halve the papaya. Scoop out and discard the seeds and membrane, then peel and slice the flesh.
Peel the banana and slice it on the diagonal.
Hull the strawberries and slice any large ones.
Stir the fruit together, coating them well with the orange juice and zest. Cover and chill overnight in the refrigerator.
In the morning, spoon the fruit into two bowls. Scatter some mint leaves over them and serve.