Drain pineapple, reserving liquid. Dissolve lime gelatin in boiling water; add 3 Tblsp. reserved pineapple liquid and cold water. Chill until thick,but not set. Pour 1/2 cup gelatin mixture into lightly oiled 6 1/2 cup ring mold; arrange cucumber slices (slightly overlapping) in gelatin. Top with rest of gelatin. Chill until almost set. Mix together unflavored gelatin and 1/2 cup water in pan; stir over low heat until dissolved. Add enough cold water to remaining reserved pineapple liquid to measure 1/3 cup; stir into gelatin. Gradually add gelatin mixture to combined cream cheese and mayonnaise, mixing until well blended. Chill until thickened but not set; fold in cucumber and pineapple. Pour over molded layer and chill until firm. Unmold.