I’m not an engineer, but it sounds like they blew up the line underwater, and it filled with sea water. Fixing a broken line on land is relatively easy. I’d expect that fixing it under water will take considerably longer. Even once the line is fixed, they’ll have to drain and decontaminate it.

If this happened to a major oil and gas company it would probably take them 18-24 months to get things fixed. I would guess that if the govt gave it unlimited resources, it would still take 3-6 months to repair... depending on the damage.