This rather charming story had me delving into my files, as mysterious crocodiles and other large reptiles have been seen from time to time, in and around Denmark and southern Sweden - rather surprisingly, as the reptilian fauna of the Nordic countries is small - the number of species is very low, and said species are definitely on the small side. Nevertheless - in the 1930's stories were being told of a crocodile in Ringkøbing Fjord, are large shallow bay in western Denmark. No trace of the animal was ever found, but some very large pikes have been caught in the same area, and they may be responsible for the sightings.
During WW2 several large snakes were making themselves known to the general public in several parts of Denmark. To day I would without hesitation have suggested they were escapees, but in the 1940's keeping large boas or pythons as pets, were hardly the thing. So what were they?
In the early 1960's a crocodile was sighted several times in Roskilde Fjord, a very long and narrow fiord stretching some 30 km northwards from form the city of Roskilde in eastern Denmark. And about 10 years later, a dead crocodile was actually found in the central section of the fiord. In 1976 yet another crocodile was found in roughly the same neck of the woods, so to speak, but in this case it was stuffed!!
The 1980's saw stories about an alligator emerging from Lake Vomb in southern Sweden, a lake also connected with several sightings of lake monsters. But, and this is most important, several of the sightings described a deep rumbling roar emanating from the lake, and in one case directly from the animal - the eyewitness even claimed the water around the alligator was boiling when it was roaring. Alligators are indeed very noisy animals, and the water around a roaring alligator does foam and fizz, so I wouldn't entirely rule out, that some idiot had put an alligator in the lake. In the 1980's more and more people were becoming interested in keeping strange and exotic pets, so it wouldn't be totally impossible.
Round about this time more and more stories about large snakes started surfacing as well, but this was almost certainly escaped or released pets, none of which presumably were capable of surviving a Danish or Swedish winter, so they were never able to establish themselves in the wild.