Ocean Simulator
Source: Drop. I found mine in the last arcane chest that i opened when hunting for the achievement (it was the 20th).
Ocean Simulator is a Battle for Azeroth toy that drops from Arcane Chests in Nazjatar, the same chests tracked by the Trove Tracker achievement.
Guide awaiting review
Travel to Nazjatar
Head to Nazjatar and begin looting Arcane Chests, which are the chests tracked toward the Trove Tracker achievement. The toy can drop from any one of the 20 Arcane Chests associated with that achievement.
Open All Arcane Chests
Loot all 20 Arcane Chests tracked for the Trove Tracker achievement, as the Ocean Simulator has been found as late as the 20th chest opened. Drop rates vary — one player received it at 11 chests, another at 20, and another tracked 58 attempts via Rarity before it dropped.
Use the Toy
Activating Ocean Simulator has a 2-second cast time affected by haste, applies a visual effect around your character, and adds ambient ocean wave sounds and occasional seagull sounds for 3 minutes. The toy has a 1-minute cooldown, allowing it to be reapplied indefinitely, and the buff persists through combat. The ambient sound slider in your audio settings must be turned up for the sound effects to be heard.
Tips
The Ocean Simulator only drops from the Arcane Chests tracked for the Trove Tracker achievement — Glimmering Chests found via Scrying Stones do not appear to drop it.
If your character has already completed Trove Tracker and looted all 20 Arcane Chests without receiving the toy, check the WoW Forums for any Blizzard bug fixes related to chest respawning, as this issue has been reported by players.