What did Logan try to say at this event?

Having checked multiple subtitle files and repeated viewings, the line is simply:

Well...
It's got water and...
It's got water.
Fuck! Fuck! (Repeated Fucks)

As mentioned, Logan was planning on taking Charles out to open seas, on a Sunseeker cruise boat. This was so Charles could finish out his life without being drugged, away from anyone that could be hurt by his seizures. Logan, the less eloquent of the pair, hurting from the loss, couldn't find anything else to say other than pointing out that Charles was laid to rest by water. It's not the ocean but its still water.

Of course, Logan is inspired by the last thing Charles said. "Our Boat...". Xavier wanted the boat as much as Logan did.

Charles' last words were 'Our boat... the Sunseeker,' the name of the boat they were supposed to take to escape. Logan's words were along the lines of 'at least there's water,' since there was a stream running alongside the grave.

I don't think you as an audience were supposed to understand that. The entire purpose of the scene was to emulate the scenarios of extreme pain and bereavement that people face. People usually don't make a lot of sense in such times. Think of it as ramblings from a person who has lost his only friend.

Even though this is a superhero movie, the general tone of the movie was meant to humanise the character of Wolverine. Notice his ageing, trying hard to avoid confrontations, selfishly looking out for himself and Charles. All this are inconsistent with the raging, jump-the-gun Wolverine we are used to. I also noticed that a lot of scenes had such incoherent dialogues. Remember the scene where Charles is dying and Logan puts him in the back of the trunk. I guess what Charles was trying to say is "Sun-Seeker" or something of that manner. All this works for the theme of the movie which tries to equate mutants more with normal human beings, with their pain, suffering and short-comings.

Symbolism/double meaning Sunseeker =charles is the son seeker. If you understand the comics and the movie charles is a mentor and like a father to all mutants and treats them as his children.

Hence why he is excited about more children being born.

Because they are like his kids and he knew how many mutants were left (not many). So he was happy about this.

But ever since his ALZ. He hasn't been able to be a father /mentor.

So he is the the son seeker(sunseeker). And he was searching for a sun in his last student(logan). Thats why the whole pop and my dad thing made it obvious.

And when he says its got water!

It means the symbolic means that charles is the sun seeker, who taking in water and sinking or sunk. Double meaning.

Also taking water in the brain is another form of Alzheimer's. Its an old saying. But saying "he has water in the brain" is a reference to ALZ

So taking water in is what happend to charles.

The water has a few meanings.

Hope this helped:)

Charles told Logan... or at least it was said that Logan and Charles would go to the sea and just be alone and be unheard or unseen for the rest of their lives... to be away from hurting others and hurt for Logan and away from it ALL for Xavier but then he does... AGAIN in a more fucked up way than when Jean killed him, so Logan pretty much was just trying to tell Charles that "This isn't what we talked about or part of our plans, I know you wanted the sea but, you're dead so I'm burying you HERE where there is at LEAST water and all like the sea", kinda like a "This'll do"-type thing, but he was so torn up he couldn't say what he had to

(My quoted sentence about what Logan was trying to say was in my own words, I wasn't quoting Logan fully, I just wanted to make sure you understood what he was trying to get at: "Here's water, it's not the sea but that's what we got so there you go, I did my best" ...something along those lines.