You can also pressure your opponent by putting Yomi Ship in face up attack position and crash it with their monster. This might force them to use their back row if they do not want their monster to be destroyed.
If your opponent has two monsters on the field, activate the second effect of Enemy Controller to your Needle Sunfish. Take control of your opponent's monster with lower attack and use Needle Sunfish effect on the other one.
Activate Hammer Shark's effect if possible, summon/special summon Lost Blue Breaker and use its effect to destroy your opponent's back row. Once you cleared your opponent's back row, your attacks now can not be interrupted, unless they have a Sphere Kuriboh on hand.
Even if your field spell Umi is destroyed, it can be compensated with the effect of Star Boy. Get over the attack of your opponent's monsters by summoning/special summoning Star Boy to buff up the attack of all your monsters. Hammer Shark's attack can go up to 2,400 with Star Boy and Umi on your side of the field.
For versatile cards which can be used in any deck, check the link below.
Levia-Dragon - Daedalus
|Once Levia-Dragon - Daedalus is summoned, activate its effect to clear all of the cards on the field, including yours, then attack your opponent's life points directly.|
Big Wave Small Wave
|Special summon Levia-Dragon - Daedalus by Activating Big Wave Small Wave.|
Moray of Greed
|Activate this card if you do not have a Hammer Shark, or if there are other cards that you need. Just make sure that you have enough monsters to defend your field, since you will be shuffling back two water monsters from your hand to your deck.|
Sea Lord's Amulet
|Activate this card to prevent your monsters on the field from getting destroyed by card effects for three turns. This card also serves as distraction for your field spell card to be destroyed since your opponent might be forced to target this card instead of Umi.|