The crew from Burnham RNLI worked alongside the Ministry of Defence when a 'bomb' was spotted in the water.
The volunteer crew were alerted to the ordinance by HM Coastguard at around 2pm on Sunday May 12.
The crew answered the call and worked alongside the MOD after a passing yacht spotted the object floating in the mouth of the River Crouch.
A spokesman for the crew said: "In response, the Atlantic 85 was launched to assist in locating the object and to keep passing river traffic at a safe distance.
"The object was located and following a full investigation was identified as a 'Trawl Bobbin' and completely harmless.
"The bobbin was removed from the river and taken ashore by the crew of the Atlantic 85 and arrived back at Burnham on Crouch station at 5:54 PM."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here