The vision of these men grabbing a large, gulping carp from the tub next to them, weighing it, whacking it on the head, then scaling and filleting it is strangely compulsive although you might not want to eat one, fish that is. Many Czechs don't like the freshwater fish, but eat it (breaded, fried with plum sauce on Christmas Eve) because it is traditional. Some aficionados though want their carp as fresh as possible so buy it live, convert their bathtub into a makeshift aquarium and do the gutting themselves for the day.
If you're staying in a hotel room or an Airbnb with a tub, we most certainly do not recommend trying this for yourself. Although that said, immersing oneself in local culture and traditions is one of the single best aspects of travelling, right? Right! Just make sure to clean things up afterwards, and please don't let anyone know you got the idea from us!