Is that spot cored?
Usually, even with a cored hull, the structural areas are solid.
Perhaps an exploratory hole drilled from the inside?
Progressive Epoxy sells a Low V epoxy that is good for injecting into cavities to strengthen. It is good because it has no solvents that need to vaporize. Tough to off-gas when enclosed inside a core. All the other penetrating epoxies have solvents to thin them.