Dominion: Seaside (Second Edition) contains nine new types of Kingdom cards, which will be released on their own as an update pack for those who own the first edition of this expansion. A few cards will receive minor errata, but these will not appear in the update pack.

The new cards: Astrolabe, Monkey, Sea Chart, Blockade, Sailor, Tide Pools, Corsair, Pirate, Sea Witch

The following cards included in the first edition should be removed when using the Seaside second edition Update Pack.
Embargo, Pearl Diver, Ambassador, Navigator, Pirate Ship, Sea Hag, Explorer, Ghost Ship