[Mariner]

“What makes those speeds so hard for the crews to endure?”

Said the man who has never cut through 25ft swells, or worse, 40ft.

The sea gets a vote on your speed.

While these ships are extraordinarily well made, I’ve seen blue water over the flight deck of an LHA...and that’s 92ft above the water line.

I’ve been hit with white water on the signal bridge at 175ft. I’ve also been on a DDG when you could see submerged water out the portal on the main deck/mess decks.

It can get so bad the skipper orders everyone to strap themselves in to their bunks for an attempt at a few hours of sleep.

Broken bones are the principal obstacle.

[xrmusn]

Also those flat bottomed LSTs, bow takes a massive dip, stern comes completely out of the water with screws squealing, then a THUD as the stern is thrust back into the ocean while the bow rises...
Two feet forward, three feet back....
Haze Gray & Underway....

True on the ‘strap ins’, used to have to strap oneself into the chair while sitting radio circuits....FUN TIMES, especially when one is YOUNG, ‘DUMB’ and BULLET PROOF...
(DUMB in this case is outwardly showing NO FEAR), no matter the situation.

[IronJack]

Look, I wasn't implying anything about the fortitude of the crews or the build of the ships. It was a legitimate question about what stresses the crew and ship endured that made those speeds unsustainable.

I know all about the sectional density of water and how hard it can feel when you slam into a wave at high speed. But I've always envisioned those warships as such huge edifices that the shocks a smaller craft would experience would just be a gnat on an elephant to them.

Apparently I was wrong. Sorrrrrrrrrrrry.