Yeah, shark won't plug even though I've tried all the smaller ones - even tried to combine two, but doesn't work either...so, after "Raleigh", it seemed much harder to get Sharky inside.
But, it seems you need to try and ram it in real hard though - then it seems to finally work...I needed a couple more tries (in Fullscreen after Downloading maybe even over a minute or two) to get Sharky's Double D-s inside and then milk him to get the stretch increase for Bezzy.