Can a river boat go in the ocean?

As long as the weather is optimal and the sea is calm it is perfectly fine to take a shallow draft boat onto the ocean, though some lake boats are better suited to that marine environment than others. A Mod V Jon boat is much better suited to dealing with ocean chop and waves than its flat bottom brother.

Why can’t river boats go in the sea?

River boats are too shallow of a draft to operate in large bodies of open water. They are either moved by a large barge or special ships designed to move other ships.