Mutated Jack

Chapter: 5 · The Boat House
Where: Boat House Storage 1F and 2F: wooden walkways with four holes down to a shallow water floor, and a single ladder

Weak point

The glowing orange eyes, about 8: face, belly, right torso, right arm, left arm, tail, under the tail and back. In phase 2, the face eye that grows back

It starts when Zoe gives you the two Serums on Boat House 2F: mutated Jack grabs Ethan and drags him into the storage room. His body has 30,000 HP but never drops below 1: only the eyes count (500–5000 HP each per the datamine; one shotgun shell pops almost any of them). Use both floors to see the hard eyes, and keep the strong ammo for the final eye. The count of 8 eyes comes from a single author: treat it as a checklist. Bring the shotgun, a handgun with Enhanced Handgun Ammo, the Grenade Launcher with Flame Rounds and the 44 MAG if you bought it; craft ammo before healing items and save in the Shed.

Reward

One Serum is left: give it to Mia (Ending 1) or to Zoe (Ending 2, which adds the "Mia (ship)" fight). Save before going upstairs to Zoe so you can see both.

30,000-HP body that stays at 1; the arms take −20%. Grenade Launcher: Flame −50–60%, Neuro −60–75%, and even so one Flame Round is worth about one 44 MAG shot. The Burner's burn does −66% and is slow to catch: last resort. 1–2 heals are enough. Madhouse: he hits harder. With the Circular Saw, circle his body on the lower floor and cut the eyes from behind or the side, where he can't hit you (another guide recommends the 44 MAG over the saw here). Keep shells or Enhanced Handgun Ammo for the last eye.

Step by step

Block (L) as soon as you land: he gets a free swipe.
Collect the storage loot during the fight. 1F: Handgun Ammo ×15 (crate, NE), ×20 (shelves, SE) and ×15 (crate, NW); Shotgun Shells ×3 (SW) and ×10 (shelves, NW). 2F: Handgun Ammo ×15 and Shotgun Shells ×10 (NW) and 1 First Aid Med on the NW shelves.
Shotgun up close (one shell per eye), handgun from afar (a few shots per eye; Enhanced Handgun Ammo triples the damage).
Flame Rounds from the Grenade Launcher for the hard eyes (belly, under the tail, back), and only while he stands still, or the round overshoots: the blast and the burn pop eyes you can't see, sometimes more than one.
Belly eyes: lure him upstairs, drop through a hole and shoot upwards. Ladder trick: a point near the ladder makes him decide to change floors; step past it, wait until he starts moving, switch floors yourself and shoot the exposed side.
Sidestep his one-arm lunge. If you see him sputtering, dash left or right: with his face damaged he vomits like a Fat Molded or grabs you.
After popping an eye, reload every weapon instead of getting greedy.
Phase 2: he dives, bursts out of the water and pins you in a corner, with a single eye left on his face. Block every overhead slam and shoot the eye between slams with the 44 MAG, the shotgun or Enhanced Handgun Ammo (an ammo crate sits on your left). It takes about 2–3 shells.
Phase 3: Zoe opens the door. As you walk to the exit Jack grabs you: press the prompt to inject a Serum. If you don't, you die.