Tracking Sea Turtles

While I am mildly excited to think of the things we could learn about the swimming patterns of a sea turtle through the experiment outlined in this article, I'm not sure how I feel about the tracking device they are using.  Is it ok to glue something onto a back of a sea turtle?  How do we know the glue is safe and won't seep into their pores through the shell?  Thankfully, the article states that they swam as if nothing was on their backs, so that calms me a little, but...  well, what do you think?