I've done it twice, in 2019 and in 2023, altho the second time was mostly Mahi-Mahi and very few marlins when I was in the water. I haven't heard about people getting gored, altho it is not entirely out of the realm of possibilities given how stupid some people are.
My opinion from my own observations and watching other people's videos is that the marlins are very "civil". They take turns at the baitball and when they see people, they veer off. I had some very close encounters but they veered off quickly to avoid a collision. It only becomes more of a free-for-all when the baitball gets winnowed down to a small size.
Mahi-mahi, on the other hand, are savages. With them in the water, at times, it felt like being in a boxing ring and getting pounded - and believe me, their heads are hard. But I think that 2023 was an unusual year perhaps due to El Niño, and if they were there in 2024, there were a lot less of them.
I think that the key to avoid getting injured is to avoid having any baitfish near your body.
That means (1) avoid swimming right into the baitball, which is what a lot of stupid people do. There are times, however, when the baitball swims at you and engulfs you. This is, I think, when you are most vulnerable because you can't see the predator and the predator can't see you. It becomes imperative to get out of the baitball as soon as possible.
It also means to avoid having the sardines use you as a shelter. Sometimes, small groups of sardines get separated from the main baitball. Having lost the benefit of numbers, they seek shelter under a boat, behind people, and I've even seen them sheltering behind sea lions. You can tell that they are there because you can feel them touch your back every once in a while. You really don't want bait dangling near your body in a sea full of predators. The easy solution is to swim back to your boat and get out of the water and re-enter once they are gone. I have been told that freediving down also rids them from you but I didn't try that.