The incident occurred on May 6, which was Encore's sea day between Seattle and Juneau. The ship was offshore, west of Vancouver Island, on the high seas. Because the incident took place on the high seas while transiting between 2 US ports and because a US citizen was involved as a victim, the US claimed jurisdiction per the Special Maritime & Territorial Jurisdiction (SMTJ).
There was no jurisdictional conversation. This one was pretty easy.
Regarding a civil claim, I'm 99.99% certain NCL's cruise contract lists the Southern District of Florida, Miami, as the designated venue.