why is it 'faire de la plongée' rather than 'faire la plongée'
Bonjour, kiki158513. See ZarrouguiL's explanation here: https://forum.duolingo.com/comment/32399340 The explanation is: **To express the fact that you do an activity, "Faire + de + le/la" is idiomatic in french. Faire du football, faire de la guitare, faire du ski...
"La plongée" is scuba diving.
Also, "faire la plongée" sounds like "faire la plonge", which is slang to say that you wash the dish. So, in this particular case, it is important not to forgot the "de".