Not quite a funnel cloud but waterspouts.
Late 80s I think on board ship approaching Gib Straits from St.Vincent.
Saw 3 double walled waterspouts (and having seen quite of number of
waterspouts over 48 years at sea, this was the only occasion of double
walls.)
We unwisely passed close to view and noted opposite rotations within the 2
walls visible with debris which also allowed timing of rotation. I recall
the speed of the inner more noticeable wall was 34 rpm and can't remember
the outer.
We were on a MetO selected weather reporting ship and the facts were
reported in the Met Logbook additional remarks at the back.
Feedback was received which I recall indicated the sighting was not very
unusual.

PeterJ