Right-click the game in your library to verify that the version number has increased.
Curse of the Sea Rats (Switch) Review - Nintendo World Report curse+of+the+sea+rats+rom+nsp+update+switch
Alternatively, if you have two Switch consoles, you can use to share the update file without re-downloading. Right-click the game in your library to verify
At launch, Curse of the Sea Rats on Switch suffered from (up to 10 seconds between rooms). After installing the 1.3.0 update : if you have two Switch consoles