Nolan Wells Death: See United Cajun Navy's Investigative Report

TMZ has obtained the United Cajun Navy's full investigative report into Nolan Wells' death ... and it includes a new photo of the three boats his friends anchored off Mississippi's Horn Island on the day Nolan disappeared.

Check it out ... the photo on page 12 of the report shows the three boats anchored side-by-side -- noted as "Boat #3," the Palm Beach and the Triton -- on the Fourth of July.

The Triton is the boat that took on water before leaving the island without Nolan.

As we previously reported, Nolan's best friend, Warren Hudson, claimed he and other friends begged him to board their vessel to leave the island around 4:30 PM ... but he refused.

The United Cajun Navy's report says the Triton left the island at 4:31 PM.

The report also shows the cluster of boats anchored up with the Triton ... and notes a woman on the island named Katelynn Brochard snapped a pic of the vessels and reported Nolan was "nowhere in sight" when her group left the island at 7:30 PM.

The last independently corroborated sighting of Nolan, according to the report, happened between 3:23 PM and 4:27 PM, and there are loads of unanswered questions about his whereabouts during that timeframe.

As you know, Nolan was reported missing and was found dead on July 6 ... washing up near where he was last seen alive.

An independent autopsy commissioned by Nolan's family listed Nolan's cause and manner of death listed as "undetermined."

The first autopsy, conducted by Mississippi officials, is complete ... but the results are still under wraps.