Jay Cooney at the Bizarre Zoology blog gives a summary of various images captured by the now defunct underwater webcam run by Scotland Online. The original article is by Scott Mardis. The webcam was pulled back in 2003 and by all accounts seemed quite popular (I was too busy with toddlers to notice). There is an online petition you can sign to persuade the owners to put the webcam back online.
My own impression was the blurriness of the objects compared to the clear images of the underwater rocks and vegetation. That would suggest to me the objects are quite close to the camera and hence small. You can see the same feature with the close up blurry, green vegetation. The other problem is similar to the problem with the dog interpretation of the Hugh Gray photograph. Where is the rest of the body?