YMS Minesweeper Deck Plans

Located in Lake Washington are three YMS minesweepers.  Two of these vessels are very much intact.  Our team has been using the below deck plans to explore these three vessels over the last several years.  These deck plans are for YMS series 135-409.

Please note that these plans should be used only for general reference.  The vessels in Lake Washington have been modified following their military use and do not fully match the structural diagrams.  Additionally, the two groups conducting penetration dives on the newest minesweeper both experienced partial structural collapse.  The latest collapse was quite serious and could easily have been life threatening.   Both dives required a zero visibility exit from the vessel.

Penetration dives on the Lake Washington Minesweepers should not be undertaken.

The below files are high resolution PDF files:

Outboard Profile

Inboard Profile & Deck Plans

Main Deck, Forecastle, Chart House & Pilot House

Survey dive on new shipwreck.

For some time we have know about a piece of debris near one of the YMS minesweepers in Lake Washington. Today we finally decided to check it out a little more. The image is a close pass with the Burton Side Scan sonar at a 100’ range. This vessel is approximately 35’ in length and was scuttled. Video of this dive will be posted tomorrow which shows identification markers. These are currently being looked-up and we will post the finding as we get them.

On this dive Shaun Gardner and Ben Griner dove to 203’ to begin the search for this vessel. Upon reaching the bottom it was clear it would be a pain to find. Visibility was poor and the murk layer near the bottom was the same color as the bottom silt layer. The effect was a disorienting search that forced us to use depth gauges and compass for reference rather than the bottom. Shaun did and outstanding job finding the wreck. Had he not planned his search patter prior to the dive we likely would not have hooked the wreck at all and wasted the dive. Shaun swam until he felt we had likely hooked the wreck and then we swam back up the line running into the bow.


The cabin area of this vessel is tight and a bag of weight used to sink this boat is blocking the door just enough to prevent access to the cabin. Additionally, the side door is rusted shut. The accessible areas of this vessel are completely stripped and little of interest remains. Shaun and Ben spent just 22 minutes on the bottom as this dive was conducted without a safety diver. Scott Christopher acted as the captain today and upon hitting the surface he had the dive platform waiting within arms reach. In all a very good dive.

Our team is not the first team to explore this vessel. Some of the early explorers of Lake Washington found themselves on this boat likely due to accidentally dropping on this site rather than the close by burned YMS minesweeper.

BurnedHull-New-Tartget-with.gifThis image shows how the target originally looked on sidescan.  The fact that it casts a shadow was the tell that the object was too large to be a tree and too long to be a rock.  This prompted us to clean up the image later when we were back in the area.

YMS Minesweeper #1(416) in Lake Washington

This minesweeper has been badly burnt. The entire upper structure is largely missing or has fallen through the decking. Puget Sound Divers has made 7 successful dives on this wreck which sits at 200’. On the most recent dive Ben Griner and Shaun Gardner dove as a team and Marc Greenway and Bob Bailey dove as a team. Marc and Bob spent 20 minutes on the wreck and Ben and Shaun spent 25 minutes. Visibility was unfortunately poor for this dive but most of the wreck was explored. Great care should be exercised when swimming over the decks as it is very easy to swim through or under objects and collapsed decking.


This dive should certainly be done at least once but with two other minesweepers in Lake Washington it is certainly more interesting to dive those.

300px-Yms324.pngClick here for more information about the YMS Minesweepers and this photo.