S.O.B. = shortness of breath. 

75 S.O.B. (50 free/10 out of water push ups/25 free no breather) means that you will swim a 50 free, get out of the water and do 10 push ups on the deck and then swim a 25 free without breathing (if you can). 

BEGINNER WORKOUT:

200 easy swim (warm-up)

4×75 S.O.B. (50 free/10 out of water push ups/25 free no breather) on the 5:00

20×25 (odd 25s back/even 25s free) on the :45

6×100 (odd 100s back/even 100s free) on the 2:30

100 easy swim (cool down)

= 1700

INTERMEDIATE WORKOUT:

15×50 easy swim on the 1:00 (warm-up)

10×25 free kick on the :40

4×50 free sprint on the 2:00

4×50 free sprint on the 2:00

4×50 free sprint on the 2:00

4×50 free sprint on the 2:00

20×25 free (odd 25s sprint/even 25s easy) on the :30

4×75 S.O.B. (50 free/10 out of water push ups/25 free no breather) on the 4:00

200 easy swim (cool down)

= 2800

ADVANCED WORKOUT:

30×50 free (10 on the 1:00, 10 on the :50, 10 on the :40) (warm-up)

20×25 free kick on the :40

12×75 (25 fly/25 back/25 breast) on the 1:30

8×75 S.O.B. (50 free sprint/10 out of water push ups/25 free no breather) on the 4:00

500 easy swim (cool down)

= 4000