Can jellyfish swim backwards?
Jellyfish move by a form of jet propulsion and it moves in the direction that the head is facing. If it needs to change direction, it just needs to pivot and propel itself in the direction that it needs to move. Comb jellies (which are not really jellyfish) have cilia that beat continuously in the water for it to move forward. So water currents are not necessary. Here is an article with videos on how jellyfish move.