How to get vorticough achievement?(Half life 2)

/ info english/ In the video shown where you can earn this achievement , there is all this after defeating helicopter hunter ,(end chapter: Water Hazard) enjoy.
/ info russia/ В видео показано где можно заработать это достижение, происходит все это после победы над вертолетом охотником,(конец главы: Опасные воды) приятного просмотра.

How to get vorticough achievement

[Emperor Swalalala III]

I was exploring the map until i found this secret.

[dao]

yes yes

[Пропащий]

the vortogaunt also talks about the end boss in hl1

[dao]

end Water Hazard

[Neobot21]

Which chapter is that?

[惡の華]

THX~

[[KA] Alleriian]

very help full XD

[1]

tnx <3