Been there, seen that and very impessive they are too.

 I made a trip from the Northern end of the loche to the south at night on a spring ebb.....not to be advised!!!!  Scotty

Hi Paul, we were in a chartered caravan on our trip, a Gibsea 37 and we were moved all about by the current in different areas of our trip down. If I recall,  the larger ones were about 4 - 6 foot accross from the sides where the water began to go down the hole.  What do you think Possy?

On our trip we were mostly concerned with rocks that were not on the Admiralty charts at that time, hence i would not attempt it again in similar conditions. 

I was a fledgeling cruising sailor at the time on a boat with a total of 6. I was the least qualified except in my youth i had done more dinghy sailing than most, but even the experienced Yachtmaster Instructors  said afterwards that it was a foolhardy exercise and they regretted the errror of their ways!

In fact I was cruising with the skipper this June and he admitted that he has nightmares to this day concerning the rocks which we suddenly discoverd were there but not on the chart when we were on the downward passage at night. 

Overall, not good skippering or seamanship but thank goodness we survived in tact. cheers, Scotty

A skipper can't be blamed for bad seamanship if he hits an uncharted rock?

Unless of course you are in the RN - remember the RN Destroyer in Australia

But I suppose they are supposed to have rather fancy sonar!