Have you looked at the Eureka Force Recon marines? There's a chap in an identical cap (cover) very similar pose to the first photo and unarmoured. ...
This guy is perfect, if there were only 3-5 more like him.
I'm a big fan of Crossover and have a couple of sprues of their baseball cap heads that I'm going to see how they look with some green stuff to make them look like the navy hat and try them on Empress Marine bodies. If they don't work out, I'll go with plan 'B' and paint the helmets black to match the vests as in the pics above.
Being ex us navy and gaming for 20 plus years, use the Eureka marines, the key is the Flat cap and obv make them more intelligent the US marine and thinner not so fat..
Well I'm going to paint up some US Marines as well, as all types of Good Guys are needed when the zombies come. As I'll be playing both, I'll leave it to y'all to decide if I play the Sailors smarter than the Marines.
Thank you everyone for all the tips.