The event is ["Clear Broken Spit of the Risen sea creatures replicating themselves" ](https://wiki.guildwars2.com/wiki/Clear_Broken_Spit_of_the_Risen_sea_creatures_replicating_themselves ""Clear Broken Spit of the Risen sea creatures replicating themselves" "). The event has been bugged with no sign of progression, the relevant enemies are all already dead. Screenshot: https://imgur.com/UW6X4BA Would really appreciate this event from being bugged so I can progress with my Treasure Hunter achievement.
This bug has been happening since last year. Get it fixed, please. It has way too many ties to achievements which gets completely screwed over because of this bugged event.