Here is the full list of all 25 Hotel Transylvania 3: Monsters Overboard trophies - there are 7 bronze, 10 silver, 7 gold and 1 platinum.
Congratulations! You’ve done all there is to do in Hotel Transylvania 3: Monsters Overboard!
Defeat the Dastardly Dragon and retrieve the final part of Neptune’s Compass
Collected every single Treasure hidden in the Lost Islands.
Unlock every single Impa Portal.
Have 30 Vampimpa at once for more than 5 seconds
Collect half of the Treasures hidden in the Lost Islands.
Hit an enemy with a ricocheted Mummimpa.
Use Mummimpa’s Magic Sand to block the smell trail from a Stinkbulb.
Have 5 of each Impa type at once for more than 5 seconds
Rescued Murray.
Defeat the Cruel Crustacean and retrieve the second part of Neptune’s Compass
You’ve successfully liberated 3 objects from Giant Clams.
Defeat an enemy with the impact from a thrown Frankenimpa.
Rescued Frankenstein.
Unlock half of all Impa Portals.
Defeat the Fiendish Flower and retrieve the first part of Neptune’s Compass.
Defeat any enemy other than a Feeble Flower with nothing but a single Wolfimpa.
Collect 5 Imparite stones in a single night.
You’ve collected the first of many treasures.
Defeat a Coconut Crab while it’s stunned.
You’ve safely retrieved an object from an angry Giant Clam.
Rescued Wayne.
You’ve defeated 5 enemies in a single night.
Unlock the third Impa Portal.
Complete the tutorial and meet up with Ericka.