I am so sorry to hear about your mother. It's a terrible thing to go through for everyone. My little sister passed away last year at 38 years old from ovarian cancer. She wanted a Viking funeral also. It is illegal, but we celebrated with a small scaled down version of a Viking funeral.

She was initially cremated, but we wanted to respect her wishes, but obviously could not do so without breaking the law. So, my father constructed a small model boat in the form of a Viking ship, it was around 20 inches long. The sail was a piece of fabric decorated with a bunch of comic character prints. (Marvel I think, she was into graphic novels and that whole scene). We added some of her cremated ashes to the bottom of the model boat. We drafted a friend with a large boat moored north of Portland, and headed to the outskirts of the islands. We had a small service for her, just close family and a couple of friends, and when it was over, we sent the model ship out to the sea, setting it on fire with her ashes in it. Being made of mostly paper, it burned very quickly and what little remained sank immediately. The boat was made of newspaper and paper mache so the remains would decompose very quickly. There was very little if any waste left behind, and what was left would have basically disintegrated rapidly.

It may not be completely legal, but it was a nice way to honor our sister with our own adaptation of what she wanted for a funeral.

Good luck to you and your family.