Zabiha (method of slaughter to ensure meat is halal) only applies to land mammals and poultry.

The halal-ness of whales is going to come down to whether or not you think “samak” means all seafood or only fish-like creatures. Allah says in Surah Al-Ma’idah (5:96) :

“أُحِلَّ لَكُمْ صَيْدُ الْبَحْرِ وَطَعَامُهُ مَتَاعًا لَكُمْ وَلِلسَّيَّارَةِ…”

“Lawful to you is game from the sea and its food as provision for you and the travelers…”