There are a plenty of (other) fish in the sea.
meaning: there are other choices (refers to persons)
magyarul: van más is a világon, van még hal a vízben
to get/find/have one’s sea legs
meaning: the ability to adjust to a new situation
magyarul: belejönni valamibe
a spit/drop in the ocean
meaning: an inconsequential amount
magyarul: csepp a tengerben
to boil the ocean
meaning: to waste one’s time
magyarul: pazarolni az időt felesleges tevékenységgel
between the devil and the deep blue sea
meaning: having only two bad choices
magyarul: két tűz között, csak két rossz közül tudni választani
to be at sea
meaning: confused
magyarul: tanácstalan
to make waves
meaning: to cause difficulty, disturbance, controversy
magyarul: szándékosan problémát teremteni, hullámokat verni
a sea change
meaning: a complete change
magyarul: óriási változás
The coast is clear.
meaning: it is safe to go somewhere or do something because no one is watching or listening
magyarul: tiszta a levegő
to have a whale of a time
meaning: to really enjoy yourself
magyarul: nagyon jól érezni magát, állatira élvezni valamit
to rock the boat
meaning: to create a problem that wasn’t there, to challenge the status quo
magyarul: megzavarni a kialakult nyugalmat, megbillenteni a hajót
oceans of something
meaning: a very large amount
magyarul: sok, jelentős, rengeteg
like a fish out of water
meaning: a person who feels awkward or unhappy because they are in a situation that is not familiar or because they are different from the people around them
magyarul: mint a partra vetett hal
jump the shark
meaning: (usually of television shows) to reach a point where something stops becoming more popular or starts to decrease in quality
magyarul: kifogyni az ötletekből
a big fish only in a small pond
meaning: to have a lot of influence only over a small area
magyarul: kis helyen nagy ember
packed to the gills
meaning: completely full; having no room to spare.
magyarul: teljesen tele van/dugig van
to fish in troubled waters
meaning: to try to win an advantage from a difficult situation or from someone else’s problems.
magyarul: zavarosban halászni
to have other/bigger fish to fry
meaning: to have something more important to do
magyarul: jobb dolga is akad/fontosabb dolga van
to keep someone at bay
meaning: to prevent someone from moving closer
magyarul: sakkban tartani/védekezésre késztetni valakit
The world is your oyster.
meaning: you can do what you want, you have loads of opportunities
magyarul: Tiéd a világ/A világ a lábaid előtt hever.
sources: Cambridge Dictionary; The Free Dictionary by Farlex
Most gyakoroljuk az idiómák használatát a következő mondatok segítségével.