It's hard to simulate the open water in the pool, but avoiding the wall during certain sets is a great way to start.

No Walls Drill: As you probably guessed, turn before you get to the wall to better simulate open water.

All Groups:

10-minute choice warm up
8-minute kick (:40 easy, :20 FAST!, repeat)

A:

6×50 @ :60 (descend stroke count 1-6)
4×100 pull @ 1:40 (3/5 breathing pattern by 50)
4×250 @ 4:15 No Walls Drill (50 FAST!, 200 cruise)
6×200 @ 3:30 (100 IM, 100 Free)
500 (rotating draft packs)
200 cool down
*4400 Total*

B:

6×50 @ 1:10 (descend stroke count 1-6)
4×100 pull @ 2:00 (3/5 breathing pattern by 50)
4×200 @ 4:15 No Walls Drill (50 FAST!, 150 cruise)
6×150 @ 3:30 (50 non-free/100 free)
200 cool down
*3300 Total*

C:

6×50 w/:15 rest (descend stroke count 1-6)
4×100 pull w/:15 rest (3/5 breathing pattern by 50)
5×200 w/:30 rest, No Walls (50 FAST!, 150 cruise)
100 cool down
*2300 Total*