One of the more indefinable fish in our theatrical waters is Shakespeare & Co., presently offering "As You Like It" at the Trapier Theater.

Into its sixth summer in the air-conditioned, comfortable auditorium but limited, low-cellinged stage of St. Albans School on the Washington Cathedral close, Shakespeare & Co. describes itself as "pre-professional," a hopeful if pretentious effort to slip out of the amateur category. Some of its choices and offerings have been painful, at variance with fairly posh surroundings, program notes and photographs.

And yet.

This "As You Like It" comes under one's favorable reservation for, once a troublesome start is past, that sunshiny comedy often reaches its proper atmosphere of humor and fantasy.

Cheerfully lit ropes, chimes and bells decorate the properly bare stage, allowing the play's episodic flow. White-tie and evening dress have been chosen to indicate the "Doook's Palace" (only twice is duke pronounced correctly), but this is outre since, Glyndebourne excepted, sunshine is no place for white ties, vests and illfitting trousers.

And yet, Eriz Zwemer becomes an amused, credible Oberon. Anne Stone provides the verve and wit for Rosalind, a most able performance. John Gilliss, as Jacques, is not afraid of that famed speech, "All the world's a stage" and director Ted Walch has used its listeners as neat accompaniment, John Cromwell, a Folger Equity regular, makes a delightful, assured Touchstone. These are well above the amateur class. SO is the movement Virginia Freeman has devised for "What shall he have that killed the deer?"

There are lovely images here, not least Zwemer's suggestion that Oberon is not fool enough always to accept Rosalind's male dress. In our unisexual climate, this is an amusing creative gambit, unspoken, but a very good actor's thought transference worthy of the best.

So, this time the cream rather outweights the water on the Trapier stage. Performances are Tuesdays through Sundays, reservations at 686-1733.