Crocs on Tisha Be-Av

Q: Is it permissible to wear Crocs on Tisha Be-Av?
A: It is a dispute. Some rule that it is permissible since one must not wear leather shoes and they are not leather. Others rule that it is forbidden since even if one wears non-leather shoes, they cannot be comfortable and Crocs are comfortable. May a blessing come to one who is strict. One who is lenient has on whom to rely.