Updated 1st November 2010; 19th May, 16th October 2011; 30th April 2012; 5th July 2015; 1st July 2018

   The original entrance (explored 3/4/10) lies about 25m north of site 978 and was pushed though a climb up, a flat out crawl then a climb down into a passage that connects with the entrance of site 978. The latter is the easier way in. The passage heading west drops down 6m free climb into a streamway which is heavily scoured with few sediments. Downstream ends at a choke and sump behind site 979. Upstream continues (from 1 to 6m wide) for about 150m to Engagement Sump with an aven above. [There is no write up in the Easter 2010 logbook.]
   At Easter 2011, the aven was climbed to where to it closed in. Also on that trip, a small passage - "on the left on the way in, the last one before you meet the sump" - was pushed for about 50m to a draughting dig. At Easter 2012, the end was described as "too low on the left and requires digging on the right. Needs surveying."
    After a couple of investigations, one a free dive attempt, the other with a small bottle, the sump was passed by Simon Cornhill in the summer, 2010 and, after 36m, emerged in a canal with walking size passage which continues upstream past a boulder collapse. The dive report (9/8/2010) can be found here.
   Over three days in August 2011 first Simon Cornhill, then Simon with Dan Hibbert dived through and pushed the upstream passage. Over 800m were surveyed: at the end sump 2 was reached and a high level which still has possibilities. (There is no log book entry.)
    Engagement Sump is 41m long with a maximum depth of 3.9m. After the initial descent from the sump pool, the passage remains in similar proportions, approximatly 2m x 2m the floor being heavily silted. The line was laid as near to the roof as possible on the left-hand side to avoid the silt. The sump is mainly heading south, passing two small airbells. The sump surfaces in a canal which was lined for a further 20m to an adequate belay. After a few more metres the canal is left and diving kit can be removed.
   A stream passage around 1.5m wide and 3 - 6m high heads off passing under a boulder collapse.
   Shortly after this, a wade through a pool and a 3m climb up on the right hand wall gains a rising traverse above the streamway. At the top of this some sandy crawls John Wayne's Sore Saddle Bags ends in a 12m aven, which must be very close to the surface.
   Back in the streamway an aven is passed followed by a couple of green stagnant pools, the main flow sinking just after these.
   The Comfort Zone continues as a fine stream passage for the next 200m, until the cave becomes more aqueous for 130m. Here a passage to the east emerges into a large 32m+ aven. A 4m climb up the south wall of the aven gains a higher level, large dry passage. After around 100m a 3m climb enters a crawl which ends in a tiny streamway.
   Back at the base of the aven a clamber down re-joins the main streamway. (The aven can be bypassed by continuing in the water, but it is out of depth swimming). Wading and swimming for the next 60m passes through a narrow rift with deep water, emerging at an enlargement with a silt bank on the west side. Swimming from here, the roof gradually lowers to a deep looking sump. (Passage description from Engagement Sump by Simon Cornhill.)

   At Easter 2012, the high level was pushed to a very small stream passage with "no way on that looks any good". Sump 2 was dived to 14.6m depth where there is a steep incline: sandy, tight and at 45 degrees. This becomes very tight and "needs digging".
   Just before the discoveries of 2011, dowsing was carried out upstream of Engagement Sump. The reactions and supposed links soon veered away from the later reality of the cave passages. This could be due to the dowsed passage not yet being found underground, or the fact that dowsing did not actually occur over where the cave passage was eventually found! Reactions were found on nearby roads and tracks and into fields. The results for the La Gatuna valley are linked below.
   A diagram of the hydrology of the San Antonio - Hornedo - Cobadal area drawn after Easter 2011 can be found here.

Link to entry in the Cave Diving Sump Index.

Reference: card; anon., 2010c (summer logbook); Corrin Juan, 2011; anon., 2011b (Easter logbook); anon., 2011d (summer logbook); anon., 2012b (Easter logbook); Corrin Juan, 2013a
Entrance pictures: yes
Underground pictures : yes : Easter 2012
Video : 2010 upstream to sump (12Mb wmv : 151Mb mpg) : Easter 2012
Detailed Survey : from Easter 2010 : from summer 2010 : sump 1 and beyond sketch : after summer 2011 : after Easter 2012
Line Survey :
On area survey : Dowsing reactions from the back of Cueva Nabo to La Collada. (Article about the dowsing carried out in July 2011 can be found here.)
Survex file : yes (Amended magnetic declination December 2013 to align with Eur79 grid and coordinates altered to fit ETRS89 datum, April 2014.)
Passage direction rose diagram: 1/7/2018