Egypt and Greece
The Egyptians were the first to understand the therapeutic properties of seawater. Hippocrates, Galen, Plato and Aristotle recommended the use of hot baths to care for and clean wounds but also for preventative purposes.
“Sun cure and sea cure are sovereign remedies for most diseases and particularly for women’s ailments” Herodotus (484 BC.)
“The sea washes away the ills of all mankind” Euripides (420 BC.)
The Romans
The Romans invented pelotherapy- mud baths made from sediment extracted from the bottom of saltwater lakes.
The solarium in roman baths served as a sunbath, as referred to by Pliny the Elder (23-79 AD) who, along with Cicero (106-43 BC), called sunbaths "sol arsus".
To restore his slaves’ strength Cato the Elder had them served seawater in wine.
As for Suetonius, he relates that Antonius Musa healed Augustus using sea baths and received the knight’s gold ring after a statue was erected in his honour in the temple of Aesculapius.
Because of the vast iconography symbolizing the sun and sea throughout antiquity, it is evident that they were seen as sacred.