If you want to operate over the water, heavy and below MinSELF - having floats is a no-brainer. MCT Ops certainly fit that profile.
Hoping it won't happen is not risk-mitigation.
It's not that simple. The H-60 family are very "dense" aircraft, and sink faster than a rock with a stone tied to it. Floatation on the classic Seahawk merely reduced the sink rate (and they were filled with helium!). Not to mention the fact that unless the aircraft was inverted while sinking, the bags were just as likely to obstruct the doors/prevent jettison.