Read the given statements and conclusions carefully. Assuming that the information given in the statements is true, even if it appears to be at variance with commonly known facts, decide which of the given conclusions logically follow from the statements.
Statements:
All streams are rivers.
All ponds are rivers.
All rivers are oceans.

Conclusions:
I. Some oceans are streams.
II. All ponds are oceans.
III. Some oceans are not rivers.

Based on the given statements, we can draw a Venn diagram:
"All streams are rivers" and "All rivers are oceans" implies all streams are oceans. Therefore, "Some oceans are streams" is definitely true. Thus, Conclusion I follows.

"All ponds are rivers" and "All rivers are oceans" implies all ponds are oceans. Thus, Conclusion II follows.

"All rivers are oceans" means rivers are a subset of oceans. While it's possible that some oceans are outside the river circle, it is not a definite conclusion from a positive universal premise ("All rivers are oceans" does not definitively imply "Some oceans are not rivers" in standard deductive logic without assuming existential import of the complement). Therefore, Conclusion III does not logically follow.

Hence, only conclusions I and II follow.