Gallery Willem – Freestyle Butterfly I Workshop [Video] 30th September 2018 BTC ButterflyLeave a Comment on Willem – Freestyle Butterfly I Workshop [Video] Butterfly I Workshop on September 15, 2018 in Rotterdam, Netherlands. This Freestyle Butterfly I is performed by Willem. Willem – The Butterfly I Instructor Freestyle Butterfly I Workshop Video Willem – Freestyle Butterfly I [Workshop] from BTC Butterfly on Vimeo.