The tugboat, identified as the Vasiliy Bekh by Odesa region’s governor, had been transporting soldiers, weapons and ammunition to the Russian-occupied Zmiinyi (Snake) Island in the Black Sea, the Ukrainian navy said.
Reportedly the vessel had been equipped with a TOR AAW missile system. that theoretically could have defended the vessel from an ASCM attack.
According to Wikipedia, Zmiinyi (Snake) Island is well within Harpoon range of the Ukrainian coast.
The nearest coastal location to the island is Kubanskyi Island on the Ukrainian part of the Danube Delta, located 35 km (22 mi) away between the Bystroe Channel and Skhidnyi Channel…The closest Ukrainian city is Vylkove, 50 km (31 mi); however, there also is a port Ust-Dunaisk, 44 km (27 mi) away from the island.