This is not a tax that is supposed to be passed on directly to the client like sales tax (or the IVA in Mexico). It is a fee that is imposed by the Marine Park. It is like the entrance fee Eco Parque Sur or San Gervasio Ruin Park collects from people entering one of those two parks. If you enter one of those parks as an individual, you pay the entrance fee at the gate. If you enter one of those two terrestrial parks with a tour, accompanied by a tour guide aboard a vehicle provided by the tour company, the tour operator bundles the park entrance fee into the price you pay them for the tour. When the tour operators calculate what price they will charge their clients for services provided, they base that price on the cost of providing that service, one of which is the cost of the park entrance fee. For dive shops it is the same process. The Marine Park fee is one of those costs involved in providing the service. If a dive operation choses to disclose the fee separately from the price of the dive, they may quote: The base price of the fee charged by the Marine Park; The base price of the fee charged by the Marine Park plus the IVA the Marine Park charges the dive operator on the fee, or; The base price of the fee, plus the IVA, plus the dive operator’s administrative costs (accounting, messenger service, etc.) involved in reporting and procuring the use permits from the Marine Park. If they choose to round it out to the closest dollar, (we are talking 3 dollars or less, right?) that seems more than reasonable to me, especially when the prices are quoted in dollars by the dive shops and US coins are not in regular circulation in Cozumel. No dive shop in Cozumel is making a killing collecting and remitting this park fee; they just try not to LOSE money doing it.