Submariner?

[Sako]

They are setting a military foot stone locally for a vet that shows
Larry A A_______
TM3 US NAVY
ISG US ARMY
VIETNAM

TURTLEMAN 30YRS US MILITARY

What does the Name Turtleman refer to? Submariner? Special type of sub? Special Ops?

[TomSudz]

Maybe a tanker (armor)?

[Clark Howard]

I would guess that it is a nickname. Thirty years active duty is almost certain to result in a moniker. Regards, Clark

[barretcreek]

Shoulda axed him a while ago.

[Former Cav]

could mean "slow" too.
we had a staff sgt everyone called "batman" back in 1966. It was NOT complimentary!

[Roadkingtrax]

TM3 is a Torpedo Man, FWIW.

[pcox]

The ISG is probably first sergeant. It could mean he served in two branches.

[boomer656]

I'm not sure what 'Turtleman' might refer to, but I'm not aware of any connection to the submarine service. If he was a TM3 on submarines, his rate should be given as TM3(SS).

[Bill D]

Torpedoman, third class petty officer (E-4). Black shoe Navy.

[Cosine26]

In my Bluejackets Manual (1944) TM=Torpedoman's Mate. Probably non PC today.
FWIW