How to put a sync cable through Ewamarine housing?

I'm planning a system where a camera with a sync cable attached is inside an Ewamarine soft housing. The cable would go through the housing and be attached to an external flash transmitter which is above the water. I'm going to use the system only in max 5-8 feet deep waters.

How can I get the Ewamarine waterproof? I have to make a hole to the housing for the sync cable to go through and the hole has to be of course sealed somehow. I'm not yet willing to invest on a real hard case housing until I study this out

Any idea of suitable glues, silicon or other stuff that might work here? The cable would stay in the housing permanently.

You could try gluing or clamping the sync port to the Ewa bag first, and use a silicone sealant that works in underwater applications (e.g. Wacker / Sika Elastosil 121).

I'd stay away from acrylic-based sealant for obvious reasons, and from organic-based sealant (polyurethane etc.) as they deteriorate with UV exposure.

Make sure you do a compatibility test in an inconspicuous corner of the bag first, and that you clean the bag free of dust, oil, etc. prior to applying the sealant.

I'm not quite sure what you are trying to achieve here, so I have some questions:

1. The ewamarine housings I have seen use a frosted plastic body material so you can see the camera within, does yours?

2. Does the camera have an onboard flash, is it to one side of the lens?

3. Does the above water flash have a slave flash sensor built-in?

If the answer to all these questions is yes then you may be able to achieve flash sync without the hole.

When you set the camera up in the housing see if you can push the bag against the cameras flash unit, look into ways to clamp the wall of the bag against the flash. Check out this wetpixle post, Gear Lust> D.I.Y. Projects> D.I.Y. Flash Sync Cable. A good length of fibre optic cable, one end butted up to the housing where the cameras flash is, the other end coming out of the water and attached to the dry flashes slave sensor should give you what I think you want.