As far as in water running ( both in deep or shallow water) is concerned I seem to remember Charlie Francis’s protocol of 2 Sets of 10x (45" Work+15" Rest).
If Your Freestyle and Breaststroke are reasonably easy to You and allow You to easily complete a 50 in the approx. time frames indicated,I would stick to that protocol as a starting point,and swim 2 x (10x50 @1’/1’15") alternating free and breaststroke each 50 to better spread the workload,and include some core/bodyweight dryland work before,or after,or in between the sets if You wish.