I think that this is a Assurance class Tug of world war two vintage,
It has tank steering, sound unit and a water vapor smoke unit,

H.M.S ATTENTIF W68

French Naval Tug.
Allocated SNO Portland for towing Bombardons.
Built 1938 Forges et Chantiers de la Gironde, Bordeaux.
L114.75’. B27.75’. 672grt. 1000ihp 3cylTE steam engine.
Armament 1x20mm AA, 2xMG.

1938 Delivered to French Navy.
19-6-1940 Arrived Plymouth.
3-7-1940 Seized and Req by RN.
9-1940 Based Devonport.
0-1940 Based at Aberdeen.
1-1941 Based at Milford Haven.
2-1941 – 1942 Based Aberdeen .
1942 – 1944 Based at Harwich.
5-1944 - 1945 Based Portsmouth.
6-1944 Towed 30ton crane 1206 Cardiff to Plymouth.
5-6-1945 Released from Overlord tug pool.
7-8-1945 Returned to French Navy, pennant A671.
1946-7 Renamed Locmine.
6-3-1964 Laid up at Brest.
The Bombardons were large 200 ft (61 m) by 25 ft (7.6 m) cross-shaped floating breakwaters fabricated in steel that were anchored outside the main breakwaters that consisted of Gooseberries (scuttled ships) and Phoenixes (concrete caissons). 24 bombardon units, attached to one another with hemp ropes, would create a 1 mi (1.6 km) breakwater. During the storms at the end 1944 some Bombardons broke up and sank while others parted their anchors and drifted down onto the harbours, possibly causing more damage (5/10)