What currency am I charged in?
You can browse prices in US dollars, Canadian dollars or Mexican pesos, but converted figures are an estimate. The deposit is charged in the currency the captain set on the listing, and checkout shows that amount before you pay.
The currency switcher is there to help you judge whether a trip is worth it in money you think in. It uses live exchange rates and it is genuinely useful for comparison, but it is not the charging currency.
Before you confirm payment, checkout states plainly which currency the deposit will be charged in and how much it will be. That figure is the one your card will be billed for; your own bank may then apply its own conversion or foreign transaction fee. The balance you hand the captain is normally settled in pesos.