The following is an abstract of the 2009 report on the wreck of HM Submarine A1 submitted by the Licensee (our own DO, Martin Davies).
There are varying degrees of sediment build up on and in the wreck, but from the measurement points taken the general levels on the outside of the hull ranges from 1/4" to 1½", this is highly mobile sediment that is disturbed very easily by the slightest movement of water.
Figure 14 shows the sample area on the port side just below the Conning tower, Figure 15 shows the sample area forward of the torpedo loading hatches and Figure 16 shows the sample area to the rear of the conning tower.
This year has seen less divers visit the wreck site and generally speaking this has only been due to poor weather that has cancelled diving activities. The wreck site is proving to be very popular with divers and there is no shortage of divers wanting to dive the site. The wreck remains in a stable condition held fast by Solent mud, with no signs of diver interference. Though on one occasion while on the site there was an indication that a group of divers were heading for A1 to dive the site, our boat and shot were circled by a private boat with divers on board, which then left the site and headed east. I am still convinced that the lack of regular divers visiting the site has kept the sites biodiversity as natural as it can ever be, and the curiosity of some species is very special when it comes to diver interaction and an observation is this has not been seen on any other dive sites nearby. The Ampelisca beds are not unique to the area but never the less are a find to be noted and again are an indication of the range of species that have been noted on the site, and the depth of the colony indicated a huge success rate in the colony and I will endeavour to investigate this further next year, with the assistance of a marine biologist.
The biggest risk to the site is from illegal fishing and the wreck remains vulnerable from lines laid by fishermen, the lines can become tangled around the wreck and attempted recovery by fishing boat and powerful winches could do extreme damage to the site and this should be stressed and reflected on in any correspondence to local fishermen. Just as divers learn to respect our maritime history so should other members of the local community who at present ignore legislation in the pursuit of financial reward at the risk of damaging or national maritime heritage.