Friends of ours stayed at the Iberostar in December. They dove with Dive with Martin and said they were NOT charged the $2 dock fee.
Iberostar charges the OP a monthly rate (or is it weekly?) for a range of divers. Not sure of the exact number but say 1 to 5 divers that month X amount of peso. You have someone diving with you one day, you pay the same as they dive with you 7 days, más o menos. It is not the per pickup, per diver charge we see other places nor is it charged to the diver.
DWM must have paid the subscription that week. SO Ibero passes the cost to the dive op and takes the hotel guests money without their knowledge.
Either the OP charges it back to the hotel guest and they become Ibero's collection agent.
Or the OP eats it as a cost of doing business, in which case Ibero is taking money from the hotel guest and ALL the other divers with that op.
Or righteous guys like Dave refuse to deal with them, making any divers at Ibero wade out to his boat.
And there you go, I am fully on the soapbox.
---------- Post added August 9th, 2015 at 02:42 PM ----------
Update: It is minimum $60US per month for a certain amount of divers. If you have one diver diving one day that month from Ibero, you pay $60. My OP generally passes the cost divided by the number of Ibero divers she has. However Ibero, because they want to hide the charge, won't accept the money from the divers themselves. So my OP had to send someone down there to pay it.
So basically do YOUR part for maintaining the wide diversity in dive ops in Cozumel and DON'T stay at Ibero.