| Date | Event | Detail | Source |
| 1799 6 January | Breaking up the wreck | HMS Fearless returns to Scilly with ‘transport ships’ to recover stores etc from the wreck of Colossus. Getting Colossus stores on board the transports takes six days, after which Fearless logs three days of ‘people engaged breaking up the wreck’ | ADM 61 4015 Fearless Log |
| 1799 20 August | Salvage by divers | Payment to Messrs TONKIN & Co for salvage £478/9/11d Iron guns (39), round shot and gun carriages are recovered by Ralph Tonkin of Penzance using early diving equipment | WO 52 130 |
| 1800 8 May | Theft of Colossus Ballast | Lt Pardoe detains an Irish sloop Tarman and finds two tons of the cast iron ballast from Colossus on board, and a further two in boats alongside. Pardoe claims considerable quantities of ballast have been removed and ‘conveyed from these islands’ | Morris 1979 p80 |
| 1800 2 July | Salvage | Payment to Samual TREGARTHEN & Co for salvage £50/13/10d One iron gun, round shot and a gun carriage are recovered | WO 52 130 |
| 1802 31 March | Salvage | Payment to Mess BLUETT & Co for salvage £83/6/6d Six iron guns, a Carronade and round shot are recovered. | WO 52 130 |
| 1808 4 June | Salvage | One gun from Colossus recovered by the use of a ‘water glass’, size and type not specified | RCG 4.6.1808 p3 |
| 1833 | Salvage by divers | John Dean & William Edwards salvage guns and copper sheeting from the wreck of Colossus. They also lose a set of diving weights, which will be recovered by CISMAS in 2019 | Hampshire Telegraph 4.11.1833 p2 |
| 1939 | Searching for Colossus | Roland Morris says he first searched for the wreck of Colossus in 1939 wearing standard-dress diving equipment | Morris 1979 p96 |
| 1950s | Searching for Colossus | The ‘archaeologist’ John Dunbar leads a diving expedition to Scilly. They search for the wreck of Colossus on Southward Well Rocks – but find nothing | The Lost Land Dunbar 1958 |
| 1974 | Colossus found | Roland Morris’ team of divers find wreckage from Colossus. They go on to recover 30,000 sherds of ancient Greek pottery as well as guns, anchors and a great many other objects | Morris 1979 p96 Williams 1980 p54 |
| 1975 | Designation | Roland Morris applied to have the wreck designated under the Protection of Wrecks Act. As with many of the early designations the stated position appears to have been incorrect | |
| 1984 | Designation revoked | Designation revoked after Morris states that ‘there is nothing left to find on the site’. Sporadic salvage continues by local divers | Morris 1979 |
| 1992 | ADU | The Archaeological Diving Unit dive on and around the designated position (1975) but find no evidence of wreck | ADU report June 2001 (01/13) |
| 1999 | Recovery of objects | Tod Stevens recovers objects from the Colossus western debris trail including part of a gun carriage inscribed with the name Colossus | ADU report June 2001 (01/13) |
| 2001 5 June | Colossus guns discovered | On a drift dive Mac Mace finds a row of cannons (which he describes as ‘big bollards’). North Dorset SAC – David Gilby, Giles Adams, Robin and Sheena Langford, John and Gwyn James -search for and find the site MM had glimpsed | (PComms 2001-2021) |
| 15 June | Site inspected | Martin Dean, head of ADU dives on the site and talks to most of the ‘key players’ on Scilly. Mac Mace recalls taking him on a tour of the site | ADU report June 2001 (01/13)(PComms 2022) |
| 5 July | New site designated | SI 2001 No 2403 The new site is over 600 metres away from the original Morris designation | Survey Report 2001 (PDF) |
| August | Survey begins | Survey of the exposed stern timbers begins – initially by photogrammetry then by baseline survey and planning frame | Survey Report 2001 (PDF) |
| September | Stern excavation | Excavation at the stern to recover a piece of stern carving (Oscar) undertaken by the ADU & Mac Mace. Time Team film the excavation | Survey Report 2001 (PDF) |
| 2002 May | Recovery of stern carving | Stern carving recovered and transported to holding tank on Tresco. Time team filming again | Survey Report 2002 p21-30 (PDF) |
| 7 June | Oscar recovery | The stern carving – Oscar recovered and placed into tank which is then lifted and transported to Tresco | Survey Report 2002 p27 (PDF) |
| June | Survey | The remainder of the exposed wreck is surveyed and recorded | Survey Report 2002 p10-21 (PDF) |
| 2 – 13 September | Excavation | Small excavation undertaken on the site of the pre-designation trench dug by MM. Extended from the Orlop, through the main gun deck and onto the upper gun deck | Survey Report 2002 p30-41 (PDF) |
| October | Time Team HMS Colossus programme first broadcast | A Time Team special is first aired in October showing the attempt to raise the stern carving in 2001 and the successful raising in 2002 | Time Team website |
| 2003 May | Sediment Level Monitoring | Recording of sediment levels around the site begins | Stabilisation Trial 2004 p6 (PDF) Sediment Level Monitoring 2014 (PDF) |
| 2003-5 | Stabilisation Trial | Three different methods of site stabilisation are trialled for a two-year period. In addition, each trial area is monitored for three months using a sub-sea data logger. | Stabilisation Trial 2005 (PDF) |
| 2004-5 | Debris Field Survey | An extensive geophysical survey is undertaken to determine the extent of the western debris field. The most promising targets are investigated by divers and the results plotted. Documentary history of Colossus undertaken by Robin & Janet Witheridge. | Debris Field Survey 2005 (PDF) |
| 2006 | Survey | Exposed timber deterioration recorded and sediment levels recorded | Survey Report 2006 (PDF) |
| 2007 | Survey | The exposed timber is inspected. Sediment monitoring points are upgraded to stainless steel | Survey Report 2007 (PDF) |
| 2008 | Recording & stabilisation | A small area at the stern of the wreck is covered with geotextile to protect the exposed timbers. Prior to covering, this area and an adjacent control area are recorded in detail (planning frame survey at a scale of 1:5). This will allow a comparison of the two areas and thus the long-term efficacy of Terram protection of timbers on this site. | Stabilisation & Recording 2008 (PDF) |
| 2009 May | Dive Trail | A dive trail for visiting divers is installed around the exposed wreckage (nine stations). An underwater guide and supporting web site are also produced | Colossus Dive Trail 2009 (PDF) |
| 2010 | Monitoring survey | The artefacts exposed on the seabed around the wreck are surveyed and recorded. The aim is to assess the impact of visiting divers on the exposed artefacts. When these objects are resurveyed in 2012, there has been little deterioration but many of the objects have moved a surprising distance. | Monitoring Survey 2010 (PDF) Monitoring & Investigation 2012 p94 (PDF) |
| 2012 | Dive trail update | The dive trail markers and sign are renewed, two additional station markers are added and the underwater guide and trail website are updated. | Dive Trail Update 2012 (PDF) |
| 2012 | Monitoring & investigation | A small area in the centre part of the wreck is excavated. No structural timbers are disturbed but recording of a lower deck gunport as well as part of the orlop deck are undertaken. An artefact reburial trial is initiated – artefacts to be recovered after 10 and 25 years’ reburial | Monitoring & Investigation 2012 (PDF) |
| 2014 | Sediment level monitoring | The sediment level monitoring points are completely replaced with improved, longer monitoring rods. The dive station floats are replaced and an additional dive station added to the dive trail to incorporate a main gun-deck 32lb cannon. New artefacts discovered to the east of the wreck | Sediment Level Monitoring 2014 (PDF) |
| 2015 | Excavation | Limited excavation is undertaken to investigate the newly exposed objects to the east of the wreck. A collection of personal items is recovered. Deadeyes and chains, as well as considerable amounts of cordage and rigging, are recorded and sampled. Gun carriage parts with ship’s name recovered. This material is the genesis of the new wrecking theory for Colossus | Investigation 2015 (PDF) |
| 2017 | Wrecking investigation | Systematic seabed searches around the wreck are undertaken, and located artefacts plotted and recorded, to test the new wrecking theory | Wrecking Project 2017 (PDF) |
| 2017 | Virtual dive trails | Web based virtual site tours of the designated wrecks of Scilly, including a narrated video tour of the Colossus dive trail | Designated Wrecks Interpretation |
| 2019 | Dive trail refurbishment | The dive trail is refurbished with new station markers and bottom lines. In addition, two enigmatic lead weights are recovered from the seabed to the east of the wreck – these will eventually be identified as belonging to the early 19th century divers the Dean brothers from their salvage on Colossus in 1833. This is the final piece of evidence in the chain leading to the authentication of the new wrecking theory. | Dive Trail Maintenance 2019 (PDF) |
| 2020 | COVID | No fieldwork | |
| 2021 September | Survey | CISMAS funded project: Search of area where Dean weights were found, detailed photography of guns (cardinal views) and sediment monitoring | CISMAS 2021 Scilly Project (PDF) |
| 2022 | Reburial trial first recovery | Recovery of 10-year reburial objects Discovery of newly exposed material to north | Colossus Reburial Trial 2022 (PDF) |
| 2023 | Recording | Recording of the newly-exposed material Sediment level monitoring Investigation of the Roland Morris site | Recording 2023 (PDF) |
| 2024 | April, Sept | Catching the Drift Geophysical survey of the suspected eastern debris field CISMAS funded project: Diving geophys targets, reinvestigating Morris pottery area and timber in western debris field. Rapid assessment of the dive trail. Investigation of iron under gun 1 and the empty gun port | Catching the Drift 2024 (PDF) Colossus 2024 (PDF) |