This boat flying is old glitch in naval strike map, it's not hack just broken game :) you should check server rules and report them in server discord/website, usually servers have rules about abuse glitch/bug but some server just ignore.

https://www.reddit.com/r/Battlefield/comments/4vvena/how_to_make_your_hovercraft_fly/

anonimosBF dude. 

1. Stop spamming report threads.

2. We don't ban for this glitch, it's a decision of the server admin.

3. Forum reports are closed, players marked as "clean" must be reported in our discord.