According to Ars Technica, Ukrainian forces used a naval drone to sink a Russian kamikaze drone boat. The report calls the engagement a military milestone in drone-versus-drone combat at sea.
The drone boat battle took place as Ukraine and Russia continue to strike Black Sea ports and ships. The report does not provide additional details on the exact location, timing, or method of the sinking.
Because this account comes from a single source, there are no independent or conflicting reports to compare. The significance, as reported, is that one naval drone has now destroyed another in combat.