Summoning multiple monsters from your hand quickly can result in a card disadvantage. This will make it more difficult to comeback if your opponent can counter them due to lack of cards that can help with more draws.
Will not be able to special summon when its level is at 1. Using A Legendary Ocean will reduce its level, making it usable 2 times only, instead of 3.
This lets you special summon Hammer Shark without using up your normal summon for the turn, allowing you to summon 3 monsters in a turn, but can only be activated when you have no monster on the field.
A useful search card to special summon a monster from your deck to find one that you need, or special summon another Hammer Shark from your deck, and use its effect to special summon another monster from your hand.
Increasing Hammer Shark's level will increase the number of times Hammer Shark can use its effect, but you will have to send your monster from the graveyard to your opponent. You can give your low defense monster to your opponent, and use Uminotaurus to deal piercing damage to it.