Skuttled in 1939 in the River Plate, are there any remnants of the Graf Spee visible?
Yes, per wikipedia: *Wreck
Admiral Graf Spee’s salvaged rangefinder
The wreck was partially broken up in situ in 1942–1943, though parts of the ship are still visible; the wreck lies at a depth of only 11 m (36 ft). The salvage rights were purchased from the German Government by the British, for £14,000, using a Montevideo engineering company as a front. The British had been surprised by the accuracy of the gunnery and expected to find a radar range finder, which they did. They used the knowledge thus acquired to try to develop countermeasures, under the leadership of Fred Hoyle at the British radar project. The Admiralty complained about the large sum paid for the salvage rights.
In February 2004, a salvage team began work raising the wreck of Admiral Graf Spee. The operation was in part being funded by the government of Uruguay, in part by the private sector as the wreck was a hazard to navigation. The first major section—a 27 metric tons (27 long tons; 30 short tons) gunnery range-finding telemeter—was raised on 25 February. On 10 February 2006, the 2 m (6 ft 7 in), 400 kg eagle and swastika crest of Admiral Graf Spee was recovered from the stern of the ship; it was stored in a Uruguayan naval warehouse following German complaints about exhibiting “Nazi paraphernalia”.*