What it does
Vehicles in Minecraft are driven by the client itself: it tells the server where the boat, horse or strider has moved. BoatFly abuses that to lift a boat into the air and fly it, while EntitySpeed pushes a mount or boat past its real top speed.
On anarchy it's a cheap substitute for elytra: crossing oceans and lava at no cost. On survival it means fast rides through other people's land; in a chase, a getaway nobody can match. And a boat on water looks harmless, so such a player is easy to miss.
How to spot it
- A boat lifts off water or ground and travels through the air
- A boat moves fast over grass or stone, where an honest one barely crawls
- A horse consistently outruns every other horse; a strider races across lava
- The vehicle drifts down slowly instead of falling
How it gets caught
The server knows a vehicle's parameters: a specific horse's speed and jump strength, the friction of the blocks under a boat, gravity. The anticheat replays vehicle physics the same way it does for a player on foot: a boat on stone barely moves, on water it's quick, on ice it's very fast — but in the air it has to fall.
The main source of false suspicion is ice roads: on packed and blue ice a boat legitimately goes many times faster than running. Others are horses with good stats, bubble columns, plugins that teleport vehicles, and lag when mounting or dismounting. So evidence is gathered over a series of rides.