Working as Mate OSV

I’m sailing on a 99 ton survey boat in the oilfield.

Wondering what it’s like working on a large OSV. If I get the
Mate OSV license, will I be on a 2-section watch?
12 hrs on, 12 hrs off?

Questions about manning on those vessels:
Typically is there a licensed engineer?
How many ABs and Deckhands?

Thanks for any insight about what to expect-

12 on/12 off
depends - some have 2 “deckhands” (1 AB & 1 AB or OS) on watch, others only have 1 (AB)
1 Chief Eng & 1 Lic Eng & Another Lic Eng or Qmed
Standing your own watch - depends on the company’s policies & your individual skill level

Thanks for the info Capt Brian!