I thought it was creative.
I did think the seaweed attacks were lame.
The Voyage To The Bottom Of The Sea tv series started out great with cool adventures. Then, the plots started getting stupid. Even as a kid, I could see the special effects were limited by budget.
Richard Basehart was Ishmael in the classic version of Moby Dick.
That weird gigantic seaweed creature that grabbed the submarine, and which they never explained! As I recall I was young enough to find it scary and creatively interesting rather than lame.