I dropped my iPhone 6 in sea water?

Dropped my iPhone 6 in sea water. It was in the water for 30 seconds. I got it out of the water, I dried it as best as i could with what i had. 10 minutes later I put it in rice, and it has been there for 2 days now. I took it out, put it in the charger. Powered it on. The battery icon appeared for 2 seconds. I heard a small bang sound, like something broke inside. And now its just dead. What should I do? Is it totally dead? Could it be the battery that broke, and that I only need a battery replacement?

Totally dead for sure

It's seems likes your phone is dead. It sounds like your battery or the circuit board in your phone has been destroyed by the sait water and when you plugged it in it destroyed it. There was nothing else you could have done it either going to work or not going to work.

You need to have it disassembled to see what happened. But because it is dangerous and there have been cases of mobile phones exploding, it is safer to ask a professional to do it. Do not do it on your own. It is impossible to understand what happened based on your question, even though you described everything in detail. A specialist should have a look at the phone. It is possible that there was an electric fault because some water possibly remained inside.

It's done. Time for a new phone.

The rice trick rarely works, btw.

Water can't move anywhere in 30 seconds.

Sea water corrodes and oxidises on the internals of electronic devices. That phone will be toast now.
Sea water is much worse than freshwater. I would not keep that phone indoors or on anything flammable just in-case the battery shorts out and causes a fire.

Sea water corrodes and oxidises on the internals of electronic devices. That phone will be toast now.
Sea water is much worse than freshwater. I would not keep that phone indoors or on anything flammable just in-case the battery shorts out and causes a fire.