If the boat is 200m away, it's probably swimable unless the current is really strong (yes I know there was a current reported in the area).
If you didn't see any activity to come and get you within 5-10 minutes, wouldn't you try to swim towards the boat? I've done it with my buddy and seen plenty of others do the same. Usually the pickup boat comes by and offers you a lift.
A 1 knot current equates to half a meter per second. 1 knot equals 1.15 miles per hour.
A modest 2 knot current doesn't sound like much, but that works out to 2.3 mph and in 5 minutes they would've drifted another 300 meters and in 10 minutes they would've covered another 600 meters or over 1/3 of a mile.
From various fin tests I've read over the years, attaining 2 mph is pretty close to the max, and I suspect those test are ambitious to say the least.
The best they could've done is to maintain position relative to the boat, but for how long could they keep the effort up?
Last year in the October issue, Scuba Diving ran an article/test concerning the effectiveness of the various signaling devices. Most worked fine to 1/4 of a mile, six foot SMB's and Storm whistles were good to a 1/2 mile, and the Dive Alert was good to a mile. This tests were all done in relatively calm waters. Factoring in the initial 200 meter reported distance the times to reach those respective distances would be approximately 3.5 minutes (1/4 mile), 10 minutes (1/2 mile) and 23.5 minutes (1 mile).
Now, I have no understanding of how or why they got out of the lagoon and why they weren't seen. Someone did make a good post that estimating distances can be tough on the water. 200 meters is no small distance anyway. Think of two full American football fields end to end. Now stand at one end and imagine how hard it would be to see someone or something laying on the ground at the other end. Now add waves.
As to the boat crew, they probably didn't look outside of the lagoon initially, as they wouldn't expect them to surface outside of it. If it took even 5 minutes to realize they were missing, there's an extra 300 meters. From what I read, the dive was scheduled for an hour, so it's not unheard of for a team to stay down an extra five minutes.
Now, about selling the story: I bet the news agencies were waiting at the hospital for the helicopter to land, with offers in hand. I understand how tempting those offers could have been, especially to a pair of "scuba bums." Let's face it, this isn't the highest paid profession they or at least he had chosen. Their biggest mistake was they should have held out for more then.
Finally, if they did conspire to do this for notoriety and a bit of cash, that's got to be a pretty gutsy call. I find it hard to believe they would've done it, but the stupidity of some has never disappointed me yet.