this (person/thing)

In the example above, the speaker uses "this" instead of "a". There's a small difference between the two. When you say "this ___" it sounds like you're talking about one specific thing. "A ___" is more general. 

You use "this ___" instead of "a" or "the" when you're introducing something specific that you're going to talk about. It's usually used at the beginning of a story or explanation. For example:

Amy and I were sitting there talking and this guy I know walked by.

I've had this song stuck in my head for two days!

Today I was talking with this girl at work who just got back from maternity leave.

In all of these examples, the speaker will continue by telling a story about that topic.

People only use "this ___" in this way in casual spoken English.

have a dream

English speakers use the phrase "have a dream" to describe dreaming. Other languages may use words like "see" or "imagine", but in English it's always "have".

a recurring dream

A "recurring dream" is one that you have over and over again. It's usually one particular situation that you've dreamed about several times. Some unlucky people have a "recurring nightmare", which is a frightening dream that they have again and again.

The word "recurring" means "happening again and again in the same way". It's also used in these phrases:

• A recurring theme in a novel is an idea which keeps appearing throughout the book.
• When an actor has a recurring role on a TV show, it means that they keep coming back on the show to play the same character.

a sinking boat

To "sink" means to fall downwards in the water.

What's the difference between "sinking" and "drowning"? First, only people can drown, while both objects and people can "sink". Second, "drowning" means to get caught under the water so that you can't breathe until it becomes dangerous.

When a boat or a ship sinks, it starts to get water inside and gets lower and lower in the water.

The phrase "a sinking ship" is sometimes used as a metaphor to talk about a company, a team, or other organization that is getting worse and worse. The speaker in the example at top said "a boat that's sinking" instead of "a ship that's sinking". One reason for this is that the listener might think that he was speaking about a company or team instead of a real boat if he said "a ship that's sinking".