If you mean a U-boat (as in Underwater boat or submarine) the answer is YES.
A blockade is a visible, open challenge, whereas a U-boat is a lurking threat, difficult to detect and carries deadly weapons.
Additionally, a blockade implies several heavy warship prepared to 'slug it out' but, a single hidden U-boat can pose the same threat and do just about the same damage.
Snow is worse than rain. Ice is worse than snow.
Hell is worse than purgatory.
It was to blocade Confederate ports and intercept war materiel from Europe.
"worse"
Worse than is perfectly acceptable; there's no single word to say worse than. Example: Her housekeeping is worse than mine. Her housekeeping is more terrible than mine. This weather is worse than expected. This weather is more miserable than expected. Or someone offered: the dreaded
Worse than Watergate was created in 2004.
The phrase 'worse than' is used in a comparative sentence.His writing is worse than mine.Words like inferior or second-rate can substitute for the phrase 'worse than'.His writing is inferior to mine.
It captured transport vessels, creating acute supply shortages
Loathing is worse.
Its' (a dog) bark is often worse than its' bite.
An alligator who attacks a bear would be 'worse than' a bear.
The word worse can be used as an adjective, adverb or nounHis condition was worse than we thought - adjectiveI did worse than I thought - adverbWorse was yet to come - noun