Cook the peeled potatoes in salted water, then dice and let cool.
Boil the eggs hard, peel, cut into small pieces and let cool.
Mix together the cucumber water, mustard, vinegar, oil and mayonnaise and mix with the chopped gherkins and smoked salmon. You can let the mixture soak through while the potatoes and eggs cool down. Mix everything together at the end. If necessary, season the salad with salt and pepper.
It tastes good immediately after preparation, but can also stand up to 2 days in the refrigerator.