Sweden may write off spy sub as net loss

What began as high drama in a Baltic bay off Sweden's most important naval base seems to be degenerating rapidly into farce.

It now seems almost certain that the suspected Soviet submarine caught spying off Musko naval base in fact made good its getaway last Thursday.

It is believed to have slipped past an underwater barrier set up by the Swedish Navy to block its exit from Harsfjarden Bay, on its way out to sea bumping into three mines southeast of the port of Nynashamn.

In keeping with its ''softly, softly'' approach to the submarine incident, the Swedish Navy detonated the mines from the shore - but only after the sub was well clear.

Meanwhile the hunt went on, with an embarrassed Navy anxious not to lose face in front of 500 journalists from all over the world who have come to Sweden hoping for a rerun of last year's incident at the southern naval base of Karlskrona in which a Soviet sub was actually captured after running aground.

The probability of anything significant being brought to the surface of the 120-feet deep bay was decreasing rapidly, however.

Comdr. Carl Svensson, the Navy's chief press spokesman, admitted that hydrophone signals from the bed of the bay picked up since Thursday could well come from old refrigerators and cars dumped by local inhabitants.

He said (to a certain amount of laughter from the assembled press corps) that loud disco music had damaged the hearing of many of the young Swedish conscripts manning listening devices, so much so that they were unable to distinguish between a signal from scrap iron and a signal from a submarine.

Shortly after he had finished delivering this piece of information Monday, a loud bang over the bay sent fast patrol boats racing across the surface.

A red-faced Commander Carlsson later admitted this ''explosion'' was in fact the sonic boom of a United States Air Force jet flying in international airspace.

Just to confuse matters still further there was a second explosion shortly afterward. This was presumed to have come from nearby rock blasting.

Then there was a third bang. This time the Navy said an automatic mine had been detonated in the southern end of the bay and that the likelihood of a submarine being found had increased. The press, getting used to things going bump in the bay, were blase. Two French journalists started a game of backgammon.

Swedish journalists were told to make ready for a special trip out into the bay Oct. 11 but the trip never came off and nobody could say why. The backgammon game continued.

The whole bizarre episode has cast serious doubts on the Navy's ability to adequately defend Sweden's long, island-studded coastline.

But Olof Palme, the newly elected Socialist prime minister, has pledged that the nation's traditional policy of armed neutrality will not be affected by it all.

However he is bound to face pressure not to put into effect pledged cuts in allocations for coastal defense funds.

Meanwhile this, according to a statement put out by Gen. Lennart Ljung, supreme commander of the armed forces, is all that is known for sure about the present incident:

''There has been a submarine within the traps (the barriers set up in Harsfjarden Bay). It might still be there but the probability decreases as time goes by. If it has escaped, it is not sure when this happened, but the period between Oct. 5-7 is of great interest.

''There has also been a submarine outside the traps. It might be the same submarine, but it might also be another one.''

The way things look from here it seems doubtful whether anyone really knows what is happening in Harsfjarden Bay . . . least of all, the Swedish Navy.

But a crop of jokes has emerged from the incident. The following is one example:

A Swedish diver goes down and knocks on the conning tower of a Soviet submarine with a hammer.

Knock knock.

From inside the sub: ''Who's there?''

''Sven.''

''Sven who?''

''Sven are you going to come up and surrender?''