Not a historian but I am an oceanographer who has spent a lot of time at sea and I was appalled at how bad the setting was. They have sailboats moving together on a flat calm sea! If there was enough wind to move the boats there would have been waves and ripples on the ocean surface. Plus, even if it was a windless night, on the open ocean there would have been swell (long-wavelength waves). As it was, it looked more like a battle on a lagoon at Disney Land rather than something set on the actual ocean.

There's a historical basis for each naval weapon used, starting with the first

1. The Ram. Rams were the predominant naval armament for millennia. Warships like the Greek trireme and medieval galley were purpose built warships. They were single sail, multi oar, shallow draft. This allowed maneuvering independent of wind and glide over the sea easily but made them unstable in rough waters. Rams were expensive to build and in many wars were defeated by merchant Cogs that were fortified.

Rams went out of favor with gun powder but enjoyed a small comeback in the early Ironclad era with ships like the CSS Stonewall

2. The Ramp, it's proper name is a Corvus. The Corvus came about during the first Punic war between Rome and Carthage.

Carthage was a naval power while Rome was a land power. Rome was capable of building a powerful fleet but lacked the tactical education. The key for Rome was to get its First Class army to fight on the sea.

Rome built ramps with a large iron spike. Roman ships would rush into Carthaginian ships, drop the Corvus and storm the ship, killing the crew. This also had the benefit of capturing enemy ships instead of destroying them. But the Corvus was heavy and disstabled an already unstable ship. Rome lost fleets to storms because of the Corvus but it also destroyed Carthaginian power.

3. Fire. The Byzantine navy had ships armed with pumps that shot the liquid inflammatory "Greek Fire" that burnt enemy ships.

The show is using ballistas, catapults or trebuchets to launch fire balls. Ballistas were used on ships but I can't remember if they were dipped in oil and set on fire.

Source: Medieval maritime warfare by Charles D. Stanton

Right. So I'm late to this thread, but I just watched the episode and would just like to drop my two cents in addition to the comments by u/XenophonTheAthenian, u/Iphikrates, and everyone else.

Like many of the tactics in Game of Thrones, the naval battle in S7E2 is silly-billy, for a number of reasons. Most make for a spectacular episode ending and great fun, but at the end of the day let's not forget this is a work of fiction.

(a) Night sailing: a thing you do not do. I actually wrote about it here. Sure, you could sail at night in open ocean, but I like to think travel in the Narrow Sea is more akin to Mediterranean Travel. Sure, maybe they had set a course for open sea and would turn towards land in the morning, but they also seem to be sailing in fog so dense they couldn't see Euron's ship until he was right in front of them.

(b) Boarding: The improbable nature the way Euron and his men boarded is discussed below. I would like to talk a bit about how a premodern navy would actually engage an enemy. I'd like to bring up one of my favorite primary sources: the Venetian Archives have a very detailed dispatch from Pietro Loredan, commander of a Venetian patrol that engaged an Ottoman fleet (in the midst of pursuing privateers from the Duchy of Naxos in the Aegean Sea, the Ottomans for unclear reasons had turned to pursue some Venetian merchantmen). According to Loredan and most other sources, steps in a naval engagement are fairly clear:

1. Pull up sails and start rowing, unless you're attempting to ram downwind (in which case you should probably start rowing anyway). Sailing is a tricky and imprecise art, and in calm inland seas you probably don't have enough wind to pull off Pirates of the Caribbean-style sailing maneuvers anyway.

2. Throw things at the enemy and hope they go away, because ramming is tricky business. In Loredan's dispatch, which I examined in more detail here, he rams and boards the "First Galley" (he presumably the most important one and not the literal first galley he sees). However, he's only able to to this at great cost: "Yet it cost me [...] for other galleys bore down upon my port quarter, raking me with their arrows. Indeed, I felt them; for one struck me in the left cheek, just below the eye, piercing the cheek and nose, and another passed through my left hand. And these were only the serious wounds, I received many others about the body and my right arm, but these were of comparatively little consequence. I did not retire, nor would I have retired while life remained in me; but fighting vigorously I drove back the attackers, took the first galley and hoisted my flag on her, then turning suddenly around I rammed a galleot, cutting many of her crew to pieces, put some of my own men aboard and and again ran up my flag [...] Their fleet fought on superbly, for they were manned by the flower of Turkish seamen, but by God's grace and the intercession of St. Mark our Evangelist we at last put them to flight, many of their men to their shame leaping into the sea. The battle lasted from early morning till past two o' clock, we took six of their galleys with their crews, and nine galleots."

3. Why are there flames everywhere? I guess this ties into the "Stratagem of Throwing Things" so remedial points are earned there, but I don't understand why or how so many of the things being thrown are on fire. Maybe it's magic? The explosions on board the ship are also difficult to explain, because I assume they don't have any explosive material on board, but I seem to recall that "Background Explosions" have been a staple of Hollywood Naval Warfare for a long time now.

(c) Ships and ship construction. The issues with Euron's Corvus have been discussed below. What I'd like to talk about is the kind of ship used for ramming. Although in Loredan's engagement, he was probably commanding a converting merchant galley presumably about fifty by seven meters in size, Loredan was also commanding a routine anti-Pirate sweep of the coast of Negroponte. During large-scale Venetian military expeditions, the Arsenal would pump out innumerable Galee Sottili, or "Narrow Galleys;" the largest of which only reached five by forty-five meters with twenty-five oars per side, each oar manned by two rowers. Although uncovered, uncomfortable, and crowded, Narrow Galleys were extremely quick and maneuverable, ideal for ramming. If Euron had been a Venetian Doge, he would have had a ton of those with him, instead of what looks like a fleet consisting of 16th century caravels.