What is the ruling on using a menstrual cup or tampons while swimming?

The basic ruling is that it is permissible for a menstruating woman to swim in public pools if the Sharia-compliant guidelines are observed, unless there is a concern of polluting the pool, in which case it is prohibited. If the cup or tampons mentioned prevent the pool from being polluted, then there is no harm for the woman in using them and swimming at that time, provided that the Sharia-compliant guidelines for a woman's swimming are observed.