Transcript for Cave divers face multiple obstacles on the last day of Thai cave rescue: Part 4

Eporter: Jason Mallinson is a man on a mission. Thrust ont to a dank ve, he needs the rain godto hold off one more day. Were you growing nervous because of the stooming? Think evebody was on edge because it had rained the night before. Reporte Chris jis anothelikely her younenthusiasticis taking part in his V So, the vy throughout the ole operation was really, really poor. Orter: Togheth two other Brits, collectively dubbedey will attempt to finish off a dramatic three-day cav R as told European ds, these we all by-name rets -- to ce in D do this. Reporter: They betterry. Y rains are threatening to scrap the plan. I mean, I think that not Ju head, lik everybody's head was like, "Hey, we're not gonna day one and E rains re start coming." Reporr: The weather is one obstac the number of people that still F the cave anotr. Four boys, one coach and four Thai military members are still inside. On day number three, we had so, O this, N mallinsoswam throu the final underwater sectiwice. I wisd never volunteere for it. To be honest, I knew ability wasoing to bad. Theso understd there just was not any other option. If the kids are Gett you saved, it's gonna have to be them who does it. Eporter: After pulling the ough the mt dangerourt of the cave's ooded section in first rescue today, Mallinson hands him off to another diver and goes back to chamber Nino gr the last boy. In chamb final water seion, Chris Jewell is hea--r three. Got his hds full rrying a boy in one hand, a guideline the other unliays one antwo, the current is strong. So,t was moving onethe boys from my left hand to my rind. I manad to let gof guideline, which cave divers useto navigate in zero visibility. Reporter: Jewel makes a motion in fort to find that guideline, butn't. Instd by the spoeam earlier in the W W jewellssumes that the electrical toward T cexit, but the stew of darknesses hopelessl disoriented and hethe wrong Y. Surfaced different section the cave and I really didn't know where I was for several minutes. I got the bot of the WER, made him comfortable, took off my cave diving equipment a was able toound four. Rr: Meanwhi mallson has suesown with the final rescue. A 13-year-old nicknamed mark. T child isre who is a really smald. Too small in fact -- for the GHT in form. It didn't fit. We put it on him, really strapped down tight so nose was tend againsface and there was a big gap under his chin we just codn't get it to sea Rorter: Rember, a leaking se means theoy could drown. So, with cng and the final D already dad, twdivers in ck deep water have to thinst. Ecide to useifferent mask.her, but I mighfo a tight sl around the boy's face. It was so nervous for me because it was the differ type of mask with thcould dislge sideway I had be so carl with him. You're eezing. You're shivering in the water. First face mask doeswork use the boy's too small. The se one doesn ha grt seal. Are you thinking, maybe we We knew we 'T have an more time and we knew this was the last option. E you set F with that kid, it was a one way journey. You weren'going back to where they started. It wasase of getng out. A bit dead or alive. Reporter: With no alternative decision needs to bee. I think it was my call, too, whether ot I was gng DI out with him or not. And I just made the call. Call is me. Thdive begins. But as sooas he's underway with his precious cargo anotr hazard. Visibility heteriorate where you could hardly see your hand in front of your face. Itas feeliine all T way out. Reporter: Low visibility means slow going. Mallinson is laser focused on keeping at mask onhe boy's face and the boy accidentalang his head againhe Wal And bec the visibility was so bad, I know I couldn't ly stop hiheng against the wall because I couldn't see his I developea where I'd pull him in really tight with his head just down here. And I'd extendhead over E top of hismy head hithe wall first and it protected his how many S do you tnk day? Dozens? Reporter: To keep them aliv Mallinson kmust keep moving. That was one of the instructionshe said, " what as fast as possib. Hypothera is going be a bighere."orter: The only guy not

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