Abstract from the paper The context and meaning of an intact Inca underwater offering from Lake Titicaca [1]:
> As the Inca Empire expanded across the South American Andes during the fifteenth and sixteenth centuries AD, Lake Titicaca became its mythical place of origin and the location of a pilgrimage complex on the Island of the Sun. This complex included an underwater reef where stone boxes containing miniature figurines of gold, silver and shell were submerged as ritual offerings. This article reports a newly discovered stone offering box from a reef close to the lake's north-eastern shore. The location, content and broader socio-cultural context of Inca sacrifices are examined to illuminate the religious and social meaning of underwater ritual offerings at Lake Titicaca.
The box was "at a depth of 5.50–5.80m below lake level" (18-19 feet) which a skilled swimmer can reach; I wonder if this might be a re-usable safe box rather than a "ritual offering".
That even seems within the range of variation of the water level. Google suggests [0] the water level rose 6m between 1943 and 1986 and generally fluctuates 1m or so each year. If that's typical, the box could have been at shore level, or well above, or 20m below in Inca times.
> As the Inca Empire expanded across the South American Andes during the fifteenth and sixteenth centuries AD, Lake Titicaca became its mythical place of origin and the location of a pilgrimage complex on the Island of the Sun. This complex included an underwater reef where stone boxes containing miniature figurines of gold, silver and shell were submerged as ritual offerings. This article reports a newly discovered stone offering box from a reef close to the lake's north-eastern shore. The location, content and broader socio-cultural context of Inca sacrifices are examined to illuminate the religious and social meaning of underwater ritual offerings at Lake Titicaca.
The box was "at a depth of 5.50–5.80m below lake level" (18-19 feet) which a skilled swimmer can reach; I wonder if this might be a re-usable safe box rather than a "ritual offering".
[1] https://www.cambridge.org/core/journals/antiquity/article/co...