San La Muerte is a folk saint that is venerated in Paraguay, Argentina (mainly in the mesopotamia) and soutern Brazil. San La Muerte is depicted as a male skeleton figure, usually holding a scythe. Although the Catholic Church has rebuked the devotion of Saint Death as a tradition that mixes paganism with Christianity and is contrary to the belief of Christ's Resurrection defeating death, many devotees view the veneration of San La Muerte as part of their Catholic faith. It has many devotee in the prison system. It has patronage over many domains, but sounds like a great figure to be used for a Cleric for the Death Domain.
A popular martyr folk saint in Argentina is known as "Gauchito Gil". He was a gaucho that was executed after false accusations. The peasants in the Pampas and the Mesopotamia ask him for miraculos healing, so it a cleric of the Life Domain may be inspirited in his myth.
There are no specific Sea Domain in DnD Fifth edition (you have this homebrew version) but a cleric of the Tempest Domain can be concepted as a practicant of the faith of the Orisha Yemanya, one of the divinities of the Yorugua people that migrated and syncretized into Brazil, Uruguay and Argentina. She is depicted as the protector of the sea and the fishes, and also a godess of fertility and womanhood.