We don't need a maritime / amphibious Brigade. It's questionable if we even need 2 RAR as it is, but who am I to question removing a unit....
The vast majority of landings conducted, ever, have been done with regular Army units. Read Kainmbla's war diary from 1944/45; the majority of units she takes are Army units - some of who Kanimbla is the first time they have seen a boat, landing craft or ship. They do rehearsals along the way. Aphibious is just another dlievery method.
Also, people really need to understand Beersheba / Keogh. They are raise-train-sustain organisations, not warfighting organisations. The Brigade we need will be assembled from 1 / 3 / 6 / 7 / 16 / 17 and others with the C2 element drawn from 1 / 3 / 7. This means that any of our units needs to be able to conduct amphibious operations (emphasised by our region). So a marine Bde would actually undermine our overall flexibility and capability (especially as, generally speaking, marine units are not as capable as land focused units).
Strike one against an amphibious AFV.
With this in mind, it flows that the forces do not need to be amphibious - rather the "bits" that move forces from the ships to the land need to be capable. They need to be able to carry lots and quickly. But they are fundamentally simple, and hence cheap to upgrade as technology increases. It is easier to upgrade a ship-to-shore connector (despite the ADFs best attempts to do otherwise) than an entire AFV or land mobility capability. Fundamentally, a ship-to-shore connector is more flexible than an amphibious vehicle, as it can move more "stuff" in a given period of time. The amphib can swim ashore (yay!), the landing craft can move a better vehicle, then do all it's stores and support in wave 2, 3 and 4.
Strike two against an amphibious AFV.
Now, tactically we need to move from the ship to the land as fast as possible. It either gets more stuff ashore, or allows us to strike from over the horizon and hence keep the ships safer. Amphib vehicles will never move fast. K-21 speed = 3.8 kt; LCM-8 = 9 kts. More than twice as fast. And LCM-8's are slow. LCM-1E go 50% faster again. And if we want to go crazy, a LCAC is 40+ kt. They are all exemplars - but anything that is a displacement hull (which an AFV is the best example of) is slower than other options like planning or hovercraft.
Strike three against an amphibious AFV.
"But Boxer is too big" I hear the cry. "It can't deploy as well". Noting that protection drives size, pending a change in armour technology or better integration of unmanned elements, all AFVs are going to be about the same size for a given protection level. But an amphib needs even more space for flotation. So pick one, an amphib has to be less protected (despite facing the same threats) or bigger (with consequences for tactical movement and deployment in confined areas like a LHD or C-17).
Strike four against an amphibious AFV.
Finally, the cost. We plan on running five 'armoured' fleets: Hawkei, Bushmaster, Boxer, IFV and M-1. They are in addition to three B-vehicle fleets. These things are expensive, and we want to add a sixth? "But it'll be smaller and cost less" I hear. You need a minimum fleet size, look at M-1. So your 40 may not be enough. So your sustainment costs will either be higher, or you cut the other fleets.
Strike five against an amphibious AFV.
tldr: Purchasing an amphib AFV goes against historical knowledge, reduces tactical, operational and strategic flexibility, undermines the basis of the Australian Army's structure, is too big, costs too much and will struggle on the battlefield, taking more losses.
Overall, it's a great example of kit fetish over needs analysis.
