I find it doesn't last as long and needs to be re-applied more, but that's probably becasue it doesn't have all those chemicals
I posted about biodegradeable sunscreen in the Yal-Ku thread
If they follow the same rules as Xel-Ha, Xcaret or Garrafon you can use Caribbean-Sol There are other biodegradeable products out there that you can use also. I recommend this one becasue they are the people that used to bottle these park's sunscreen that was sold at the parks, so I know it's acceptable.
They say you can use anything that says biodegradeable on it and doesn't contain any of these things:
Octocrileno Benzofenona Butil metoxidibenzoilmetano Hexilodecanol Dimetil capramida Cetil dimeticona Metilparabeno Polietileno Propilparaben Butilcarbamato.