. It’s a lot more than a dribble – a good couple of inches at the deepest point of the boat. Even when the boat is stationary in the water, water is coming in fairly quickly, but not quick enough for me to be worried about the boat’s seaworthness. It seems to stop at around the couple of inches mark (presumably level with the sea), although I was bailing it out fairly frequently.
The plug is firmly in, so I don’t think the water is coming from there. I mollcoddle the boat when launching/beaching and it has no dings or scrapes on the underside, or signs of the tube fabric coming away from the fiberglass hull.
The only other potential weakspot I could think off is the hole where the bolt goes through. I noticed that the wing nut was a little looser than the very tight I do it up when inflating the boat, presumably because the rubber had expanded in the sun and was then cooled by the cold water. However, the back of the boat still filled up after I’d tightened the wingnut again.
Does anyone else who owns/has owned an F-RIB have any ideas where the water might be coming in
? If not, I’ll try inflating the boat in the garden next weekend, pouring water in to the back section and seeing if it drips anywhere. The boat is under a year old and has been used less than 20 times, so hopefully it's something that can be fixed under warranty if there's an issue that's not a simple DIY fix.
so simply removed it and applied more marine grade silicone which cured it 
. I'll buy and apply some silicone to bushes and drainning fitting/plug and see if that sorts things out. 
. No signs of cracks, fortunately!
