I had a problem with a guide in Seychelles because she didn't turn up (her name is Sheena) and at the end she wanted to get paid and refused to accept my full refund (for a tour she declined)…! Viator was very correct and professional because they refunded me. So, the tour operator wanted to cheat, but Viator was correct and reliable. I highly recommend and I will continue to book through them. Viator can obviously be also affected by unethical tour operators.