Giordano at no point is suggesting Robyn was kidnapped.
In his interview he is being asked up front why did he bring up the human traffickers?
Giordano then responds:
While I was in prison, some of those prisoners had told me that that location (Nanki) is very dangerous, currents and so on, and also mentioned that boats come from Venezuela and they drop of illegals and they swim the rest of the way in, and they mentioned several of them did not make it to shore, because it is dangerous there, so that is the knowledge I have.
So, IMO he is clearly trying to point out here that it is not uncommon for people to drown at Nanki.
at 05:15 into the video:
http://abcnews.go.com/GMA/video/gary-giordano-takes-critics-15082306
He continues to say the police had told him there was a boat out there (at Nanki), that he himself had not seen a boat, it was the police who mentioned to him that there was a boat out there and that they were investigating it.
Giordano only knows Robyn never made it to shore, that when he reached the beach he did not see her anywhere nor was she found shortly thereafter.
If the police then claims the presence of a boat and wants to pursue some boat scenario who is he to object to that.
That is not Giordano suggesting Robyn was kidnapped, he just lets the interviewer know what the police told him. IMO