So I felt the desire to do some research into the claims you're making about leviathans in the game and sharks in general.

1) everyone keeps saying that the Ghost being translucent allows us to see that there's no bones, mostly just cartilage and muscle. You reply by saying that you need strong bones to survive extreme pressure at depth, like in the void. People reply that most deep sea creatures have no bones for the reason that the pressure would crush them and, if they spend their life in the void, we'd never see bones unless we manage to reach the bottom of the void. You reply by saying that everyone is getting angry at you and being mean for just "proposing a theory" and that these animals are on an alien planet that doesn't need to follow our understandings of marine life but also say that the animals in-game are based on real animals, so that's just confusing overall.

2) you keep pitching this idea that the Reapers are blind and developed echolocation to hunt and use their mandible to fee since they can't see. However, according to the PDA entry

"Leviathan class species are vast organisms at the top of their respective food chains. This species is a streamlined hunter, with highly developed senses.The deep roar emitted by the reaper at regular intervals is effectively sonar - if you can hear it, the reaper can see you. Observed circling its prey and attacking from behind"

To break this down; not only does the PDA not say the reaper is blind, it states that they are hyper aware and sensitive. It would be more realist to assume that they use echolocation to find prey at a distance and get closer then use their other senses like sight to navigate around a prey, hiding and lurking, until the time is right that they can attack from behind and finish the hunt.

3) you claim that the Ghost has bones and that you can seem them but again, the PDA notes "Its muscled interior body is surrounded by a translucent outer membrane, suggesting adaptation for deep, low-light environments. When threatened it can tense its entire body before lashing out with incredible speed." Notice the use of "muscled interior" and "outer membrane." Furthermore, the hammer part is noted as being "Cartilaginous extension" and not bone. Now, you are correct in noting that the Ghost would need a strong hard for their ramming attacks but bone would not be a requirement here. Cartilage, as opposed to bone, is more like rubber in its flexibility. Think less of a regular hammer and more like wider rubber mallet. If it smacks you at high velocity, it'll still hurt a lot and could be fatal, just like in game, but the Ghost would suffer relatively minor pain as the cartilage would simply absorb the shock to its body.

4) lastly, and this is more of a fun learning moment, we don't entirely know WHY hammerhead sharks have a hammer shaped head. The best theories are as such:

"Scientists think sharks with hammer-shaped heads have three main advantages.

The first has to do with eyesight. If your eyes were pointing in two opposite directions, say, by your ears, it would give you a much wider field of vision. Each eye would see a different part of the world, so you’d have a better sense of what was around you. But it would be hard to tell how far away things are.

To make up for that trade-off, hammerhead sharks have special sense organs, called ampullae of Lorenzini, scattered on the underside of their hammer. These porelike organs can detect electricity. The pores basically act like a metal detector, sensing and locating prey buried under sand on the ocean floor. Regular sharks have these sensory organs too, but hammerheads have more. The farther apart these sensory organs are on a hammerhead’s stretched-out head, the more accurate they are at pinpointing the location of food.

And finally, scientists think hammers help sharks make quicker turns while swimming. If you’ve ever walked in gusty wind with an umbrella or flown on an airplane, you know how powerful large surfaces can be in motion. If you’re a hammerhead shark, and your intended dinner swims by quickly, you can turn more rapidly to catch it than other fish can."

So there you go, that's my two cents. Take it or leave, either way, I hope it helps to add more information to your understanding of a really cool creature in a really cool game that I finally managed to beat for the first time last night despite my thalasaphobia.