suggestion...
Crispin,
There is a great deal of difference in compliance between your mask's silicone, the glue, and the hose material. I recommend you try some kind of 'hard' joint instead where the silicone mask around the hole you punch is mechanically compressed so it doesn't leak.
A possible solution is to use a 'barbed-stem-to-male-thread-fitting', which may be found at your local hardware store, or an industrial catalog like McMaster-Carr's. (mcmaster.com, see item 5454k42, may be too small.)
1. punch a hole in your mask slightly smaller than your threaded fitting.
2. push the threaded fitting through the hole from the outside (ocean-side)
3. get a nut with corresponding threading and tighten it down, compressing the silicone mask in between so the mask itself acts like a gasket
4. attached appropriately-sized hose to the barb outside
5. attach hose to mouth - voila
Just my 2 cents.
Peter