I would assume he has heard of Oceanus, how much he knows is another question. He is also aware that this temple is actually dedicated to an earlier deity, Oceanus is simply how it translates. Roll Int+artes liberals to see how much he recalls.
Int 2 + AL 3 + roll 9 = 14
He recalls a lot about oceanus, pretty much all that is known- the titan who originally represented the entirety of the seas, he is believed to be representative of a pre-Grecian deity, his sister is his consort, and she is the mother of rivers and the nymphys. He did not participate on the side of the Titans in the struggle between the titans and the Gods.
Paphos will relay this to Antonius and Julia, along with the idea that the actual deity is someone predating Oceanus. The Romans were big on co-opting and conflating foreign deities; it looks like that tradition goes back even further.
Edit: He'll add that if the whirlpool leads to Oceanus' palace, the cave might lead to Hades. Not sure about the third boundary.
"This is very interesting... Hermetic magic seems unreliable here. Perhaps this place is so ancient that different, long forgotten laws are to be obeyed here. I am afraid I will only be able to assist you with simple tricks, and that you will need to guide us all", says Antonious.
"Oceanus you say, Paphos ? Hum, if the ruler of this palace is a Titan or the incarnation of primordial power, we will need to be especially ... careful with our words as to not anger it." What do you say we explore the temple, its denizen will probably be able to tell us more about this island, and will probably be able to tell us what is the way out."
the temple is not very large, and you quickly ascertain that there is nobody else on the island.
"three choices then, first the palace through the whirlpool, second the tunnel, third the boundary. I suggest the palace as most likely to gain an explanation of this place. I would happily accept magical transportation if you are able, otherwise I am a decent swimmer."
"I agree with your assessment Paphos ?"
To Julia:
"What do you think my dear friend ? Shall we go into the temple ?"
If Julia agrees to go into the temple, he will help Paphos to reach the Whirlpool with a rego corpus spell, as well as cast a rego aquam ward of diameter duration on all three before they cross the whirlpool.
"Do you mean the palace? Of course."
The group flies out to the whirlpool, and enters the water just outside the pool. Julia takes the lead in plunging into the whirlpool, then seems to be focusing her attention on the destination.
After falling through what seems like a sea surrounded by odd greyish bubbles for one minute, the group finds themselves in the courtyard of a great palace made of coral. There are trees swaying gently, more as with a tide than a breeze, and fish floating by through the trees. And women, young naked women, frolicking everywhere.
The group will walk toward a group of young women.
"I am Antonius, this is Julia and this is Paphos, an talented artist. Excuse me, but we involuntarily stumbled upon your palace, which is very" He is distracted, "... attractive." His eyes open wide, realizing what he just said. "I mean full of wonders and a source of amazement to us. Fish dont fly where we come from, nor do they float in the air. Can you tell where we are ?"
Several of them giggle,on esteps forward. "Welcome to the sea palace, tell me, what strange place do you come from where people have such odd configurations of their skin?" she gestures to your clothes.
Well, when in Rome and all that. Paphos will disrobe to "blend" into the crowd. While he is nothing special physically, He carries a sense of gravitas that somehow owns the nude look as his own.
Note that he is not especially attracted to the nymphs; he is far to aligned with the earth to fall for the charms of the sea.
Antonius looks at Julia, stunned, and then at Paphos, with a look saying 'No way I am getting naked'.
"These are called clothes, and what I am wearing is a leather jerkin. They protect us from the weather and the sun, and harm. We come from an island called Matla, located in the Mediterranean sea, between Europe and Africa. More precisely, we come from a very old temple called Tarxien, although its name might have changed over the centuries. If this is a palace, to whom does it belong?"
(Does Antononius see vis ?)
Every one of the girls contains vis, probably as might. The fish contain vis. The nearby horses contain vis.
"It belongs to our father, king of the sea." Then different girls give different names at the same time, Enllil, Yam, Yah, Oceanus, Neptune, and Poesiden being easily recognizable.
"Is today a special day for your Father? We were in a temple once dedicated to His glory and found ourselves in this place. Is there anything special going on right now?"
"Besides the Neptunalia?" (July 23rd, making the adventure technically mid-summer, but dang it, it fits so well...)
After seing vis everywhere, Antonius is starting that they are in fact not in a magical regio, but in the magical realm proper. He will inquire to the young woman.
"I rembember correctly, it is a festival in the honor of Neptune. I know we are unnanouced visitors, but would you like to give as a tour of the palace ? Maybe, we too, could participate in the celebrations of Neptune, if you wish us to, of course. What is your name, by the way, I was too rude to ask you, sorry."
"I am Orseis, please, follow me, Many of my sisters have gone to collect the sacrifices, though we do not get as many as in years past."
Antonius will raise an eyebrow at the mention of sacrifices:
"What kind of gift would be fitting for the owner of such a palace ? I am afraid we are empty handed right now, and though there is little we can do about it, but if we happen to come back here again, I would like to know what to bring to thank your father for his hospitality. You say they have diminished over the year, do you know why is that, if it isnt indiscreet ?"
Orseis shrugs "Meat, sometimes horse, some chariots. more recently it has been smaller things, a lot of coins have gone into his sacred pools, some artwork, especially small marble pieces for some reason. As to why? I don't know, they have been declining for a very long time. He doesn't seem worried about it though. So what do you want to see? The stables, the orchard? Let me guess, the throne room. Everybody wants to see the throne room."