Thanks to our rock-star quality interlibrary loan staff here at the University of North Dakota, I was able to get my greedy mitts on F. Halkin, "Saint Leonide et ses sept compagnes martyrs a Corinthe," EEBS 23 (1953), 217-223. This little gem of an article will help me complete (or at least fill out) some thoughts I offered a couple of weeks ago in this blog post (and in a related post here). Just in case you can't be bothered to click through to either of those links, I suggest that the prominent baptistery on the coast at Lechaion may have particular significance to the site. In short, if this is a church dedicated to St. Leonidas and his companions, then a baptistery (and references to water) would have particular significance since the saint and his friends were martyred by drowning off the coast.
The Late Byzantine (or later, at least, post early-13th century) life of St. Leonidas published by Halkin in the 1930s includes a couple references that would appear to support my argument. I'll include paragraph 8 below (p. 223):
While I won't translate the entire passage, I'll offer a quick translation of two sections (note that my translations were tweaked in the comments!). First, beginning at line 5:
UPDATED: Dimitri Nakassis provided this nicer translation:
"So with much time having passed and with the public executioners having started sending Leonidēs down into the Gulf first, he [Leonidēs], having raised his face to heaven, said, “Behold! And with this second baptism today have I been baptized, which makes the man within us more clean.”"
Also then at line 12:
UPDATED: He also offered this: "Pious men, dragging the bodies of the saints lying on the beach, having attended to them in honor they buried them, having built a church on the spot, where [the bodies], both augustly worshiped and extolled everlastingly, to those who approach faithfully they make to gush out healings each time."
According to Halkin (and I have no reason to doubt it) this is the only reference to a church built to honor Leonidas and his martyrs in the accounts of his martyrdom (p. 219). The text that Halkin presents here is almost certainly post-13th century in data and pulls information from a range of known synaxaria and a few other lost sources. One of this unknown sources preserved -- it would seem -- some memory of the great church on the Lechaion coast. Moreover, the clear and explicit link between drowning, baptism, and the massive baptistery at Lechaion might even hint that the building preserved in the memory of this text is not the church, but the baptistery. The baptistery may well have stood longer than the church to its south and considering the relatively shallow depth of the excavations at the site, it seems plausible to assume that significant parts of the buildings on the coast were long visible.
The goal of all this speculation, of course, was to understand the link between the Lechaion basilica and the elaborate nymphaion located less than a kilometer to the south of the basilica along the coastal bluff. This structure shares many decorative cues with the Lechaion basilica and I have proposed (very tentatively) that the shared emphasis on water brings together the Corinthian wide theme of the well-watered city and the specific circumstances of Leonidas and his companions' martyrdom. This is just another, albeit very small scale study, of how religious authority projected into the Corinthian landscape.