MÜGGENBURG and MARGRIT HBK 92 (and an unnamed barge) on the bottom of Grevenhofkanal at low tide, seen from Ellerholzdamm, Hamburg, 29.03.2020

MÜGGENBURG is the former Hamburg harbour police launch WS 29.
Built in 1959 by Ernst Menzer shipyard, Hamburg-Bergedorf, yard no. 417.
Decommissioned in May 1977 and sold to private interest.
No info about the time between 1977 and 2005 other than that she was laid up at Hamburg-Harburg for many moons...
In 2005 she surfaced again as MÜGGENBURG (probably sold to a new owner).
On February 4th, 2015, she made her first trip in many years... and her last. She began to take on water, but the master managed to reach Landungsbrücken and evacuate the boat before it finally sank.
She wasn't salvaged before February 10th and is rotting away since then...

Some data on MARGRIT HBK 92 (Thanks to David Asprey!)
Built 1973 by Lübbe & Voss Werft, Ihlow/Westerende-Kirchloog
(situated on Ems-Jade Canal)
Gt: 38
Loa: 17,26 m / Lbp: 15,53 m
165 kW
Fishery no. HF 562
Call sign: DNIM
7/4/2003 retired from fishing register
so presumably changed after that to HBK92 (=Hamburg-Kleinfahrzeuge)