Sidharth Kaushal on Inside Science Podcast

Early indications suggest that the attack was conducted using an un-crewed service vessel laden with explosives, not unlike some of the vessels the Ukrainians have used to harass Russian ships in and around Sevastopol, for example. Although, given the size of the explosion and the likely pay load it might have carried a larger pay load. Of course, this is based on early indications, it would carry explosives along probably on a pre-programmed route to the location it was meant to detonate.