BioShock Infinite
80 Achievements
1,695
42-52h
Bon Voyage
In the Main Campaign, killed 20 enemies by knocking them off Columbia.
25
How to unlock the Bon Voyage achievement in BioShock Infinite - Definitive Guide
If you are past this point, or didn't get the achievement yet, you can load up the aforementioned chapter and finish up from there. You do not need to hit a checkpoint to save your progress, simply keep reloading until the achievement pops.
You can do this slightly earlier by using a combination of buccing bronco then undertow while an enemy is fairly close to the edge. If your undertow doesn't push him straight off, wait until he stands up again, or he'll just bounce the railing until he dies from your undertow.
I loaded up Beggar's Warf, which is the checkpoint at the end of this area (in the video shown above), turned around and went back to the nearest floating ship where there is a guard patrolling, and started meleeing guys off the edge quite easily.
There are also some boxes you can hide behind that put you in an excellent spot for this.
Use Shock Jockey first and then Undertow on the enemy NPCs to knock them over the side of the aircraft. I found this a good method for progressing with the 'Bon Voyage' (25G) achievement as well as the 'Hazard Pay' (25G) and 'Skeet Shoot' (25G) achievements.
Just keep reloading your most recent checkpoint and following the steps until you've killed enough enemies and the relevant achievement(s) unlocks :)
Firstly, you will need to get the "Undertow" Vigor, so please see Well Rounded for all Vigor locations. Once you have it, tap to fire a jet of water at enemies and knock them off edges. This works best against enemies on zeppelins and barges. There is a zeppelin that spawns right after you first obtain “Undertow”, and there is a particular section of the game late on where you fight a large amount of enemies on barges, making this trophy very easy to obtain.
This trophy can be farmed by restarting checkpoints or replaying chapters. An easy method to earn this trophy earlier in the game has been found by Terminator:
After you find the Gunsmith's Tools and go through the Tear, you will come to an area with two Sky-Lines. The enemies will jump on the Sky-Line and come after you, so get them to follow you then do a Sky-Line Strike on them whilst they're over the big hole in the middle of the map. Reload the Checkpoint as needed.