Besides the formal distinction between sea and land, and the process of territorialization of adjacent waters, a more complex social process of sea/land exchanges and conversions takes place. This process leads to semantic shifts as material immaterial transformations. Our contribution discusses socio-semio-ethnographic notes and qualitative data collected in a recent fieldwork investigation (January-February 24) of collective representations of the relation with the sea among the Moken (Surin Islands) and the Urak Lawoi (Ko Lipe) of the Andaman Sea. The case studies show the process of social change “between land and sea” in a context where this so colled Sea people are entangled in complex dynamics involving natural parks, industrial fisheries and profit-oriented tourism.One of the emerging issues concerns the traditional way of disposing of waste that the use of plastics undermines. The Moken have now been forced to live in villages on stilts on the beach. And the pile-dwelling in addition to being their home is also from where they dump their waste for the tides to catch, but it comes back to them on the beach. And the national park as a state institution pays them something to collect the plastic. Thus a special relationship is created with plastic waste; also of a ritual type. More generally our paper aims to show not only this phase of fieldwork but also to sketch the way trash and waste enter a circuit of both a traditional culture and transformations of this same culture in relation to institutions, tourism.