Very much so actually.

The Navy was in general against the idea, and instead supportive of a continuation of the strangulation and bombardment of the Home Islands.

This was the result of the coming together of several factors. One is that King and Nimitz at many times had a fundamentally strained relationship with MacArthur, and his rather rosy assumptions about the invasions nature and conflicting intelligence did little to raise their opinion of the plan with him in charge. There is also the rather sanguine prospects for a large fleet standing off invasion sites Experience off Okinawa had taught the Navy that even if the vast majority don't get through that a handful of suicide weapons can till exact quite a heavy toll, with an even larger presence expected off the Home Islands. It is unlikely that Japan could have defeated an invasion outright but it would not come cheaply.

King and Nimitz essentially agreed to hold off making a fight of it in the Spring of 1945 as the plan was still taking shape and was still several months away. While their opinions did not change it is clear that had the bombs and Soviet intervention not ended the war that there was the possibility it became quite the blowup. With FDR King and Marshall had often made efforts to keep their disputes below the level of having to go to the President as sometimes he would make a choice which pleased neither of them. But with the positions of power reversed it is an interesting thing to consider how Truman might have reacted with an open acrimonious split in his 2 senior most officers.