I will tell you if you want to go down range but are hesitant about SWCC or SEAL then by all means, you need to get into the NECC (Naval Expeditionary Combat Command) as Seabee, EOD, RIVRON, or any of the numerous Expeditionary Security units.
If you don't want to be a Seabee rate or EOD Tech then the safest bet is as an MA. the unit you spoke of before MESF is almost entirely MA and some GM's. The problem with GM is that there are alot of them on the big gray floaters. Chances of a GM going to a ship are better that him going anywhere else his first term.
With MA you will have a high likelihood of going to an Expeditionary Security command or, more so, an installation command to do security for a year or two (GITMO, Bahrain, anywhere) to learn how to patrol or do prisoner handling. Those are the skills that are going to set you up to call you detailer (guy that gives out the change of duty orders) and negotiate.
This will answer JimMCpog's question too. Negotiating for orders is when a person is soon to complete an assignment and calls the detailer who has the big list of jobs out there. The more shit you've done as far as quals and good evals the better chance you are at getting those orders you want like RIVRON or Inshore Boat Unit or Mobile Security Squadron.
RIVRON is now looking at E4 and E5's to fill their ranks. The likelihood of you going from boot to there is slim. You will need some experience. They are also taking SWCC washouts so you might want to look at SWCC again, LOL.