Ridiculous in what sense?

We've known of Archimedes' Principle since about 250 BC, so there was never a question whether metal ships would float. The real question was "why metal", what possible advantage does it offer over wood?

Today it may seem like a no-brainer that metal is stronger than wood, but that wasn't always the case. Iron is pretty weak, brittle, hard to work. It has less "give", so the stresses and strains of wave action wear it down. It rusts on contact with seawater, it attracts marine life, so the ship becomes encrusted by barnacles which slow it down. Making water tight metal joints is hard, it doesn't swell like wood to self-seal joints.

Because of these reasons, there was no obvious need to switch to iron. The earliest metal ships were from the 15th century Joseon kingdom (Korea), but they didn't actually use metal as a structural material. They were wooden warships with thin metal skins whose purpose was to protect the wood from incendiary arrows. Fire protection.

In the 19th century, Britain, the US, Germany and Italy began building metal warships. But they faced big problems because of the reasons I mentioned earlier. Those 12 or 15 inches of wrought iron were great against muskets or small shot, but they were brittle and easily cracked by heavy shot. And hard to repair in the middle of the ocean, under fire. They were heavy - too heavy for sail, so you really needed steam propulsion to make them viable.

As a result, many iron ships of this era weren't really iron at all. They were sandwich ships - wooden core for structural strength, iron layer for armor, another thin layer of wood on top and copper plates outside to slow down rusting and poison critters that attach themselves to ships.

True iron hulls had to wait for developments in metallurgy. Steel came first, but steel was also too brittle. Then came "Harvey Metal", which was case-hardened nickel-steel alloy, that finally made metal hulls practical and brought the cost down. Then there came Krupp Steel, which was Harvey Metal, but with chromium added for more strength, and then Improvef Krupp Steel, which used a gas cementing process to make it even tougher.

So the "ridiculous" part of early metal was that in most ways it was worse than wood for ship building. The needs of war slowly made metal practical, first as fire proofing, then as projectile armor, and eventually for structural strength.

My understanding is that early sailors didn't like it. Iron ships were heavy and clumsy. They were seriously underpowered unless you added steam, but steam engines were incredibly noisy and dirty and belched smoke. And even with steam, their top speeds were slower than fast sail ships. Of course, on the upside, you were never becalmed when the wind died, you could chart a straight course from A to B without zigzagging or tacking against the wind, so metal ships powered by steam still broke speed records.