One YMS Identified, Another YMS Identity Narrowed

Of the 3 Minesweepers at the bottom of Lake Washington, only the YMS-359 was positively identified since their discoveries (the YMS-359 has 359 painted on the bow).

Now the guys over at are reporting they have identified one of the other two minesweepers and narrowed the identity of the third.

The least intact YMS in the lake is now identified as the YMS-416.

Short history on the YMS-416:
“Laid down 9 January 1944 by the Stadium Yacht Basin Inc., Cleveland, OH; Launched 28 May 1944; Completed 21 October 1944; Struck from the Navy Register 7 February 1947; Sold 6 December 1947.” Fate (previously) unknown. At some point this one was stripped and scuttled.

The YMS we discovered most recently looks like it may be the YMS-118, -124 or -311. Here is a short history on those three ships:

YMS 118 : Struck from the Naval Register, 17 April 1946; Sold in 1951 to the Northland Navigation Co., Ltd. of Vancouver, British Columbia, Canada, rebuilt as a general cargo vessel and named Pacific Prince; Sold 31 January 1962 to Skeena Navigation Ltd. of Vancouver; Sold 31 March 1962 to the Northwest Shipping Co., Ltd. of Vancouver; Sold 16 June 1966 to Fred S. Hill and John R. Keebaum of Seattle, WA and rebuilt as a fishing boat and renamed V-O; Sunk in February 1967 in a voyage from Seattle to King Cove, AK.

YMS 124: Laid down, 4 December 1941 by the Krause and Banks Shipbuilding Co., Inc., North Bend, OR; Launched, 6 June 1942; Completed, 23 October 1942; Struck from the Naval Register, 17 April 1946. Fate unknown.

YMS 311: Commissioned USS YMS-311, 6 November 1943; Decommissioned, 31 July 1946 and placed in service as a Naval Reserve training ship; Named Robin and reclassified as a Motor Minesweeper, AMS-53, 1 September 1947; Recommissioned in February 1952; Reclassified as a Coastal Minesweeper (Old), MSC(O)-53, 7 February 1955; Decommissioned 7 December 1957 and placed in service as a training ship at Tacoma, WA; Placed out of service in the summer of 1961; Struck from the Naval Register, 1 August 1961. Fate unknown.

I tend to believe the most recent YMS to be discovered is the YMS-118 because the wreck we are diving has clearly been rebuilt into a fishing vessel. Note square windows of pilot house in prior posts – square windows are not ‘original equipment’ for any YMS as they all had round bomb-blast/porthole type windows.

The inconsistency with calling this YMS the -118 is that it reportedly sank in route to Alaska – so how did it end up at the bottom of Lake Washington?

YMS Penetration

In the last three weeks we’ve had a number of dive teams on the YMS doing initial exploration. The wreck has now been penetrated in a number of areas, but so far no designation numbers or other identifying marks have been found.

The primary points of entry have been in two areas: the pilot house and the main cabin below the pilot house – with both areas offering further pentration opportunity once inside.

In the case of the pilot house, there is a small room aft that appears to have been used as sleeping quarters. The space is very tight, with various debris making exploration difficult.

In the case of the main cabin, there is an additional door forward which has not yet been breached, and a small opening with ladder that leads staight down into the belly of the ship. This lower deck beneath the main cabin has now been explored, both forward and aft. We had hoped that there would be a path that lead from these rooms below the main cabin back to the engine room, with an exit opportunity through the hole in the stern deck where the engines were removed. Unfortunatley this is not the case. The path forward leads to a deadend as would be expected this close to the bow, and the path backward appears to lead to a solid wall – possibly a firewall separating the engine room from lower sleeping quarters.

The lake visibility has been particularly bad the last three weeks, but the interior visibility of this wreck has been completely horrible. We have divers talking of not being able to see their own 18W HID lights, rust and other particle matter continously falling from the ceiling, errant wires hanging about, it is just generally a nightmare in there. 100% of those that have entered the room below the main cabin have exited via touch contact with the cave line they established on the way in. Very dangerous.

JaWS Diver Scott Boyd (, who is known for taking some of the best underwater wreck photos ever captured in Lake Washington, was on the wreck this past Sunday as my dive partner, but we’re all going to have to wait until the visibility clears up before we get to see any of his photos.

I include a photo below to show established & expected penetration paths. ‘X’ marks a known deadend and ‘?’ marks paths yet to be explorted.

(click to enlarge photo)

Underwater Photos of YMS

We put two teams of divers on the ‘new’ YMS the last day of 2007. It is a fantastic wreck; truly one of the best in the lake.

We spent 25 minutes at depth and left feeling like there was a significant amount left of the wreck to explore. As mentioned before the engines, weapons, pilot house controls and various brass components look to have been removed prior to sinking, but otherwise this wreck is intact. Plus there is a signifanct amount of debris throughout.

The Pilot House still holds a knocked over filing cabinet, the bathroom is complete with head and cabinetry and there are various other artifacts inside cabin rooms, on the stern deck – including two large generators, and on the bow.

One thing we have not yet found is any designation numbers indicating which YMS we might have. Determining whether numbers can be located will be the focus of future dives.

Some images, taken from video shot by SCRET diver WJ, included below (click to enlarge):






More reports on this one to follow. We’ll dive it fairly actively over the next few months.


US Navy Minesweeper Discovered in Lake Washington

This past Sunday, in a joint effort between JaWS Marine and Innerspace Exploration, we located a previously undocumented Navy Minesweeper in Lake Washington. This ship is 130ft in length, 24ft wide and is sitting in 200ft of water off Sand Point/Magnuson Park.

The YMS designation stands for Yard class Mine Sweeper. These ships were used during WWII for near shore mine sweeping as means to prepare for amphibious based assaults. More detailed history on the YMS located here and here.

Dive and ROV operations have not yet begun on this ship, so we do not yet know which of the 481 YMS ships built during WWII we have located. Based on experience with the relatively well known YMS-359 also located in Lake Washington, as well as other submerged minesweepers, we’re hoping the white designation numbers will still be visible on the bow.

Included below are a few sonar images from our work on Sunday, as well as some YMS 3D modeling images courtesy of Infusion Studio’s 3D.

A few things to look for when comparing our sonar images to the model photos: the narrow, but tall pilot house, fenders on stern deck (these reflect very brightly in the sonar image), opening in hold where ‘spool’ use to sit, opening in hold at engine compartment (meaning engines were removed prior to sinking), forward mount for guns.

More on this one as the story unfolds; I hope to post underwater images here before the end of the year.