Looks like the ACV is really happening
How about this photo series recently posted by the U.S. Indo-Pacific Command, showing operational Marine Amphibious Combat Vehicles (ACVs) at play from a big ‘phib.

An amphibious combat vehicle with Battalion Landing Team 3/5, 11th Marine Expeditionary Unit, launches from amphibious assault ship USS Boxer (LHD 4) in the Pacific Ocean, Sept. 14, 2025. Elements of the 11th MEU embarked Boxer to conduct integrated training off the coast of Camp Pendleton, California. (U.S. Marine Corps photo by Cpl. Joseph Helms)

A U.S. Marine Corps amphibious combat vehicle with Battalion Landing Team 3/5, 11th Marine Expeditionary Unit, conducts an open-water transit prior to embarking the amphibious assault ship USS Boxer (LHD 4) in the Pacific Ocean, Sept. 14, 2025. Elements of the 11th MEU embarked Boxer to conduct integrated training off the coast of Camp Pendleton, California. (U.S. Marine Corps photo by Cpl. Joseph Helms)

U.S. Marine Corps amphibious combat vehicles with Battalion Landing Team 3/5, 11th Marine Expeditionary Unit, prepare to embark the amphibious assault ship USS Boxer (LHD 4) in the Pacific Ocean, Sept. 14, 2025. Elements of the 11th MEU embarked Boxer to conduct integrated training off the coast of Camp Pendleton, California. (U.S. Marine Corps photo by Cpl. Joseph Helms)
Based on the Italian Iveco SuperAV 8×8, the BAE-produced ACV is the replacement for the troubled and long-serving (circa 1972) AAVP-7A1, the last of the Marine Corps amtracs.
These guys:

The legacy AAVP7.. AAV7A1 assault amphibious vehicles transport Marines with 2d Assault Amphibian Battalion and 1st Battalion, 2d Marine Regiment, both with 2d Marine Division, for a wet-gap amphibious crossing as part of a company-sized infiltration on Camp Lejeune, N.C., Aug. 10, 2021. The infiltration focused on maneuvering across complex terrain and picket lines with near-peer capabilities in an unscripted force-on-force scenario. (U.S. Marine Corps photo by Lance Cpl. Jacqueline C. Arre)
Whereas the 29 ton AAVP-7A1 was a giant (26 foot long, 11 tall and wide) bread box that was clad in 45mm of armor and was good for 45mph on surfaced roads and 7 knots in the water, the even heavier (32 ton) and larger (30 feet by 10 by 10) ACV can carry about half the personnel (13 Marine passengers vs 21) but can at least do it faster, with a published speed of 65mph on paved roads and 6 knots on the water.
The Corps announced the delivery of the 300th ACV at its BAE production facility in York, Pennsylvania, earlier this month. That’s about half of the way to the finish line of 623 vehicles, based on the latest program of record, to equip its three active and one reserve Assault Amphibian Battalions.