Worse things happen at sea.

One way of cheering people up is to make them realise that other people may be in a worse situation.

You’ll miss the boat.
Hurry up!  (Here boat is used for any opportunity.)

Don’t rock the boat…
or don’t make waves
are advice against upsetting people by suggesting new ways of doing something, for example.

We’re all in the same boat.
Boat here is situation or circumstances.

Plain sailing.
Usually this is used with negative connotations.  I recently heard a difficult marriage described as “It wasn’t all plain sailing.”

That’s taken the wind out of your sails.
Someone said something which deflated someone else’s ego, perhaps.

Ships that pass in the night.
People who live or work near each other, but never meet are described this way.

When your ship comes in.
Ships used to be the main way of importing valuable cargo, so this was often said if someone was dreaming about something they would like to do, if only they could afford it.

Plumbing the depths.
Does this come from measuring the depth of the sea?  It is often used figuratively maybe about searching memory.

I’m all at sea.

Nail your colours to the mast.
Coloured flags are used as signals.  If you nail your colours to the mast, you say what you believe.

There are plenty of other sayings based on the sea and sailing and a wealth of literature.  A writer who was inspired by the sea was John Masefield, whose poems, “Cargoes” and “Sea Fever”, are well know.  His “cross-over” book “The Bird of Dawning” is also well worth reading.

The Sea of Galilee is mentioned in the Gospels.  Two notable occasions are first when Jesus was asleep in the boat and a storm blew up.  The disciples woke him and he stilled the storm.  Matthew Chapter 8 verses 23 to 27  The second one is when he sent them on ahead in a boat and then walked on the water to join them.  Matthew  Chapter 14 verses 22 to 33

Another book I’d like to recommend is “If you want to walk on water, you’ll have to get out of the boat” by John Ortberg.