Let’s take a bitesized look at how to say ‘the sea’ in Irish.
The Irish for ‘sea’ is farraige /farr-ig-eh/.
As this is a singular feminine noun in the nominative, when we add the definite article an /un/ we add séimhiú (aspiration). So, in order to say ‘the sea’ in Irish we say an fharraige /un arr-ig-eh/.
Let’s look at how to talk about different qualities of the sea.
Colour of the sea is dath na farraige /dah nuh farr-ig-eh/.
Temperature of the sea is teocht na farraige /tyowkth nuh farr-ig-eh/.
..and seabed is grinneall na farraige /grrin-ul nuh farr-ig-eh/.
In these last three examples ‘an fharraige’ is in its genitive singular form ‘na farraige‘.
When we want to use the word ‘sea’ to name a particular sea, such as the Caspian Sea or the Baltic Sea, we use a different word in Irish: muir /mwirj/.
So, the Irish Sea is Muir Éireann /Mwirj Ayr-unn/.
A different word again is used when referring to a particular ocean. That word is aigéan /a-gay-un/.
And so if we want to say the Atlantic Ocean we say an tAigéan Atlantach /un tah-ay-un At-lon-tukh/.
Let’s finish up with a seanfhocal, or proverb, relating to the sea. These wise words of warning are ná déan dánaíocht ar an bhfarraige /naw din daw-nee-ukth air un varr-ig-eh/. This means don’t make bold with the sea.
Check out Niall and Eoin’s favourite seanfhocail (proverbs) in this fine video.

Go raibh maith agat, a Ben 🙂
As to the Irish seanfhocal – is there any other figurative meaning in the English language besides that of ‘don’t make bold with the sea’?
Haigh a Anna,
I think that this seanfhocal refers specifically to the sea. There isn’t any figurative meaning that I detect.
Le dea-ghuí,
Ben