This can be done in almost the exact same way as my guide in "All creek, No Paddle" and takes about 5 minutes. Ideally, you can get both achievements in one with this guide!
Firstly set up a custom Solo battle Vs AI with roughly similar traits:
Teams: 1v1
Enemy Team: Hard or Above
Generated Map: Warring Islands
Starting Age: Age III
Map State: Revealed
Starting Resources: HighOnce you're in-game, get a dock built and a few basic resource incomes, now start pumping out Demolition Ships from the dock. It will take about two detonated ships to blow up their galleys and above. However, we're on the lookout for their
transport ships.
The achievement is not to destroy five ships in one as I'd originally taken it as, but any five enemies total at once! This can easily be done by sinking a full (or partially) transport ship. With the revealed map you can see their movements. Take a group of 5-6 demolition ships and place them nearby.
Be on the lookout for a transport ship with troops (you can see its capacity overlaid). If you manage to get a transport ship that is full showing 16/16 you will also net the 'All Creek, No Paddle' achievement at the same time.
Sink that ship and the achievement is yours!