If I wanted to die in a viking funeral, like getting put on a boat and set ablaze while I am in the middle of the sea can this be done? Or is it even legal?

So you want to die in a burning boat‽ While some countries in Europe allow for assisted suicide, I don't think any allow for self immolation while at sea.

Now if you're looking for a viking funeral procession after your death, I would think environmental regulations would be the biggest hurdle.