So the fin box in my board has an issue. Where the side of the box meets the bottom of the board there's a split. It's like the bottom of the board had come away from one side of the box. Think a split running the length of the box on one side and about 2mm down.
Now the box is still very solid in the board and the only really issue I can see is after a sail if I push down very hard on the bottom of the board I can squeeze a tiny amount of water out and there a slight clicking noise.
It's been like this quite a while, and doesn't seem to be getting worse. So my question is this, how do I stop water getting in? Can't patch it as it would make the box to small so I was thinking I could drill a few small holes in the base of the board along the side of the box and inject something in there like gorilla glue?
what do you think?
www.gorillatough.com/product/original-gorilla-glue/

It's roughly where the green line is. This is not the box in question

Its unlikely that it is leaking as the box sits in a block of closed cell high desity foam. Just to clarify is the crack in the box itself or is it between the top laminate of the board and the box?
I would try to inject epoxy in there but would be reluctant to drill holes.....a photo would help.

Looks like between the top laminate and the box.
I think the water is just sitting between the top laminate and the block of closed cell foam the box sits on. It's really a tiny amount of water I get out.
im guessing the top laminate has lifted very slightly and is not glued to the closed cell road any more?
can't get it to show up in a photo.

If its the glass delaminating from the box, not uncommon as nothing bonds well to thermoplastics and they don't rough up and/or clean the box enough in the factory.
As a temp fix and only if its minor (still touching the box), once its dried properly some superglue along the edge will suck in with capillary action and seal it.
But if its lifted like a bubble and/or more than a couple mm from the edge, proper fix might be adviseable

Just noticed the second green line - there also....?

No the short green line shouldn't be there.
it's lifted very slightly maybe a mm at the most.

Soak in some superglue and push down. If it doesn't get heavier, you're good as gold.

When you say super glue you mean something like this
www.gorillatough.com/product/gorilla-super-glue/

Yup - any non-thickened cyanoacrylate. The little tube that you can get for $2 is the same stuff as the name brand though