LT FUBAR
I don't see it in this picture and it may be that this is a different version, I don't know. Ours had seals in the one and only passenger door. The door seal was mounted in the frame and surrounded the door. It, as well as the others, was activated by the pilot (left seat) using a round knob. The seals were swelled by compressed air from a tank that was fed by the compressor mounted on the main transmission. (Compressed air also powered the wheel brakes) These seals were located around each window in the cockpit, the radome, the bomb bay, as well as the door. Our aircraft was the ASW version and I assumed, perhaps wrongly that the accident aircraft also had the seals. I know that there was a SAR version of the MI-14 and I would think that they would want the seals also. Ours had no inspection port.
As for the radome, you are right about the numerous screws or bolts holding the fiberglass dome. But ours had the inflatble seal.
When we flew overwater, the drill was to shut all the openings, seal them, and insert air conditioner hoses into our flight suits since we didn't have the appropriate air conditioned suits.
In my opinion, if there was nothing more than just rubber gunk around the dome to seal out water, just a little deterioration and some hefty water pressure would cause a major leak.