HMS Colossus - dive trail

The Ship

HMS Colossus was a Courageux class 74 gun warship built in 1787 at Gravesend and wrecked off Samson in the Isles of Scilly in 1798. The Courageux class ships were built from the lines of the French vessel Courageux captured by HMS Bellona in 1761. The 74 gun ship was one of the most successful types of the period. They were typically about 51m in length with a crew of over 600. During her relatively short working life Colossus saw action at Toulon, Groix, Cape St Vincent and Cadiz.

A diver exploring the Colossus Dive Trail

In December 1798 Colossus was on her way home to England with a remarkable cargo including eight crates of Greek antiquities, wounded sailors from Nelson’s victory at the battle of the Nile and the body of a dead admiral. What she did not have on board was one of her spare bower anchors, which had been given to Nelson’s ship Vanguard in Naples. This would prove to be disastrous. She was sheltering from a gale in St Mary’s Roads when the anchor cable parted and she was driven aground to the south of Samson. All but one member of the crew were taken off safely before Colossus turned onto her beam ends and proceeded to break up.

For more information about the wreck of HMS Colossus and the work which has been carried out on the site see our Projects Page and Download Centre.


The Dive Trail

In May 2009 a dive trail was added to the wreck of HMS Colossus.

This dive trail consists of numbered observation stations situated around the site and a waterproofed underwater information booklet which guides divers between the observation stations, explaining the exposed remains and detailing brief background information on the wreck.

The strern wreckage of Colossus and the diver trail. The area shaded in blue has been protected using geotextile matt.
The stern wreckage of Colossus and nine observation stations encircling the site. The area shaded in blue has been protected using geotextile mat.

You will arrive on the site from a permanent mooring situated 20m to the north-east of the wrecksite, from which you will follow a fixed lead line from the mooring block to the first observation station and an underwater sign. The underwater guide then directs you around the site, via the numbered observation stations, arriving back at the first station and underwater sign at the end of the tour.

A seabed station and visiting diver

The observation stations are placed at points of interest around the wreck, as shown above, and consist of a numbered buoy floating about one metre above the seabed.

The numbers on the stations correspond to a description within the underwater guide and are also shown on a site plan on the front cover of the guide. At the end of each description a compass bearing and distance is given, allowing you to navigate to the next observation station.

Each station also includes a direction arrow indicating the location of the next station.

A seabed station and visiting diver


The dive trail was extended by three dive stations in 2012 and 2013. The new layout of the extended dive trail is shown on the plan below.

Dive Trail

The dive trail extension begins at the seabed sign (station 1) and is marked by leaded line fastened to the seabed.

sation 12

The 32lb Blomefield Gun at station 12

You can watch a video of the new dive trail here

Diving HMS Colossus

Ongoing monitoring of the sand levels around the wreck of Colossus has shown that the wreck continues to become exposed. Once the timber of the wreck is exposed on the seabed it begins to deteriorate. Consequently, the exposed timber of the wreck has a relatively short life expectancy – so enjoy it while you can.

The wreck of HMS Colossus is designated under the Protection of Wrecks Act 1973 which requires that you be in possession of a visitors' licence in order for you to visit the site. If you dive the Colossus with one of the three local dive charter boats operating in the Isles of Scilly you will have a visitors' licence organised for you. The charter boats also have copies of the underwater guide which you can use during your dive. Information about each of the local charter boats can be found below.




Moonshadow Jo Allsop
Morvoren Tim Allsop
Tiburon Dave McBride


The area of geotextile matt and a seabed sign on the Colossus wrecksite

An area of protective geotextile mat and the seabed sign on the Colossus wrecksite

The underwater guide is available as a Download and bound copies are also available from the Isles of Scilly Museum on St. Mary's.


If you have any comments regarding your dive on HMS Colossus we would like to hear from you. If you have any photographs, or perhaps a brief account of your dive, that you would like to see on this website please Contact Us.

The HMS Colossus dive trail was funded by English Heritage.


English Heritage




HMS Colossus

A memorable dive
Debris field survey
Site stabilisation
Dive trail
Site plan