Early naval battles mostly revolved around ramming and boarding, and early naval cannon were mostly anti-personnel weapons. But by the 16th and 17th century, cannon became powerful enough to punch through the hulls of enemy ships. At around the same time, propulsion shifted from oars to sails, freeing up space on the side of ships to mount large gun batteries.
Now it was at least technically possible to defeat your enemies from afar - if your aim was good enough. In practice, many battles still ended up happening at close range. Depending on range and intent - to sink, to slow, to disable, to kill enemy crew in preparation for boarding - a wide range of different projectiles were called for.
Iron Shot
Your basic cannonball: a single sphere of iron, shot from a cannon to smash into the enemy ship.
In naval battles, very flat trajectories were preferred to maximize the chances of hitting the target. At close range, double-shotting was sometimes employed. Two balls in one cannon meant double the damage at the cost of a massive reduction in range and accuracy.
These projectiles weren’t a snug fit: cannon balls and cannon bores both had irregularities from limitations in their manufacturing. So balls basically bounced along the bore when fired.
Stone Shot
An early kind of "explosive" ammunition made of stone cut into spheres. It would shatter on impact, leaving jagged holes in the hull and injuring anyone nearby.
Canister Shot
A metal cylinder filled with lead or iron balls. The case would disintegrate immediately after firing, spraying shards and projectiles in a conical pattern, like a giant shotgun. This was extremely effective against enemy crew, but only at close range.
If proper ammunition was scarce, canister shot was sometimes made of random scrap metal, rocks, and any other hard things that could be found lying around. This was referred to as scrapshot or langrage.
Grapeshot
So called for its resemblance to a cluster of grapes, this munition was similar to canister shot, consisting of a number of smaller balls held in a canvas bag. It, too, had a shotgun-like anti-infantry effect, but the balls used were generally fewer and larger, which made them more effective against masts, sails and rigging.
As with iron shot, canister- and grapeshot would sometimes be double-shotted, to devastating effect. To avoid bursting the gun when firing, the amount of powder used had to be reduced, which made double-shotting only effective at very close ranges.
Chain Shot
A specialized form of ammunition, chain shot consisted of two iron weights linked by a chain. When fired, the chain would extend and sweep through the target ship, taking down masts and rigging and cutting the occasional crew member in half. This allowed ships to slow down or immobilize their enemies, to be able to out-manoeuvre them, or as a prelude to boarding.
Part II