Potential Risk 1; The teenage friends could drown in the river as they are drunk.
Harm Minimisation; Adults could come and supervise and would therefor take the drinks off the kids and get them out of the water.
Outcomes of strategy 1; due to the parents coming along and supervising the teens. There wold be no alcohol which would therefor mean that no teens would get drunk and sick. Which would also mean that the teens would not drown or hurt themselves on the beach.
Potential Risk 2; the teens could become drunk and drown at the beach in the water.
Harm Minimisation 2; to reduce the harm that might occur with the teens, they could relocate so that they aren't near water, and preferably around adult supervision.
Outcomes of strategy 2; if the teens relocate to a place where they are supervised and not near water then they are not at risk of drowning or becoming severely ill. They would also be supervised by adults who would know how to help in alcohol involved situations.