@ragecagez
That's a pretty big list. I'd say there is more added content than original content.
As said by @DominusOcto7 megalodons, skeleton ships, ghost ships, and tall tales were all added. The legends of the sea expands on the Easter eggs that were in the game as well as ones that were added later, giving rewards for finding them.
There are new voyage types, new factions, new types of treasure, alliances, brigantines.
A new volcanic sea was added and some existing islands were changed. An uncharted island turned into the reaper's hideout, the spire in the center of the world had the sea dog's tavern built upon it, and old boot fort was cursed and turned into the fort of the damned.
We have more instruments and shanties to play. We have cursed cannonballs and chain shots. Firebombs and blunderbombs that can be fired or thrown.
Rowboats, harpoons, harpoon rowboats. Expanded ship customization, expanded ship damage, and a long list of new cosmetics including emotes, curses and pets.
Last but certainly not least, we have the supply crate.
If you're thinking about returning, you're wasting time thinking when you could be sailing.