Monean research vessel
A Monean research vessel was a type of spacecraft used by the Moneans during the 24th century. It was armed and capable of travel through both space and water, to depths up to a hundred kilometers. They posed no threat to an  starship and could be easily destroyed. 

The  encountered at least three of these vessels while in orbit of "The Waters" in 2375. ()

de: Moneanisches Raumschiff
Starship classes