Thanks for that edit specifying, that helps a lot! Naval warfare in the north sea and English channel was very much different from better known Mediterranean combat.

Firstly TL:DR anti-personnel missile weapons followed by boarding was the primary battle tactic.

In the rough Atlantic and North Sea, the more sophisticated tactics of the Mediterranean were generally not used (though the French often imported Genoese galleys and crews.) Ramming was far too risky in the rough and icy waters, since it often sinks both ships. Heavy catapults or ballistae were nearly impossible to aim, and the heavier northern ships hulls were much less vulnerable to them. Greek fire wasn't used in the North. The historical records do include something like a "soap bomb" which was thrown onto the enemy deck to make it so slippery the crew would be at a disadvantage in a subsequent boarding action. So that left them with various missile weapons all designed to thin out an enemy crew, bows, crossbows, slightly larger crossbows fitted to the deck or rails. As on land, the English longbow was a favored weapon of that nation during the Hundred Years War. But the vast majority of northern naval action was done by boarding action and melee combat, normally from bringing vessels alongside an enemy.

As for boats and strategy, northern fleets had two basic ship types, viking-style clinker built galleys or longships, and much larger sailing vessels, Cogs or eventually Carracks built with frame construction. The sailing vessels were much larger, with taller sides that gave them considerable advantage in repelling boarders. The galleys were generally faster and more maneuverable, they could decline battle with Cogs or Carracks if needed and appear with more surprise (at least over short ranges). Both types used primarily sails for propulsion, although longships/galleys could use oars in tight places or dire need.

Strategies were much constricted by the difficulty in successfully finding an enemy fleet and intercepting it in open sea. Compared to the Mediterranean, and the later age of sail, keeping on a station was much more difficult and dangerous. Instead, battles were much more often fought between ships in a harbor or estuary being assaulted by a force from seaward. Since navigation was difficult, ships (especially galleys) stayed close to land. This lead to choke points like "The Trade" at the tip of Brittany where English convoys going to Gascony (the only French province remaining under English control until Agincourt) would need to make their seamarks. Lastly, many Northern territories had poor roads and land communications (Wales, Brittany, Denmark, Norway and Scotland in particular) so communications by sea were essential for the successful operations of any army, especially an invader.

Source: "Safeguard of the Sea: A Naval History of Britain 660-1649" by N.A.M. Rodger

1: Artillery. Anything from small torsion based delivery systems like balista and scorpions to full blown trebuches have been used- in the 12th and 13th centuries Chinese sea powers would use trebuches to lob gunpowder bombs at each other. We also know the Romans would use catapults.

2: Light missile weapons. Bows, arrows. I doubt crossbows would see too much use because of their physical limitations.

3: Chemical Weapons. The Byzantines employed Greek Fire. While it's composition is lost to history, we do know that it behaved similarly to Napalm, and that they employed it like a flamethrower.

4: Suicide Craft. Small, light, and fast ships could be stuffed full of gunpowder and other explosives and sent at the enemy fleet. Typically, dealing with it was incredibly difficult. Couldn't ignore it, but firing on it was never a safe bet. Similarly, it wasn't that unusual for crafts to be lit ablaze and sent to ram enemy craft.

5: Ramming. Many ship battles in the Golden Age of Greece involved long, narrow ships with metal tipped heads that would be intentionally rammed into enemy ships. While you wanted to hit the broad side of an enemy ship, because of the nature of ship construction at the time- wood as the primary material- even head-on collisions were devastating. "bumper boats" isn't exactly the right phrase here.

6: Boarding crews. Anything from wooden plants to rope bridges and grappling hooks could / would be used to get your soldiers to their boat.

Ship combat has a lot of variation prior to the development of ship borne cannon. You'd probably get a better answer if you had picked a specific time period, and a specific region.

You should note that gunpowder weapons were used in land battles during the 14th century, so I wouldn't be surprised if they were used in ships as well.