Which Gorilla glue you talking about ... polyurethane or PVA?
I believe that both would be non-toxic when cured, but I am not sure of submerged use. The PVA (white/cream color) is only water resistant ... I use it for my outdoor project, but it will fall apart if continuously submerged. The polyurethane (brown bottle) is more water resistant, but I still won't trust it in fully submerged applications (it is rated HPVA type 2, not for continuous submersion.) Epoxy or silicone is better choice IMO.