Why Caliban specifically mentions "sun is the keyword"?

It's pretty obvious that Caliban can't stand sunlight, so why would he want to live cramped with two other people in a small boat?

For Logan and Xavier would be fine, they could go up to the deck and enjoy the good weather, swim or fish.

Even if it's a large yacht, in case anything bad happens he either drowns or dies of the effects of sunlight on his skin. He doesn't seem to be very happy about this idea.

Caliban and Logan are talking about leaving. Logan says "us", but Caliban clarifies "you and him" (Logan and the Professor, i.e. Caliban isn't going to be going with them):

Logan: Money to get us out of here.
Caliban: No, not us. You and him.
_Source

The name Sunseeker is a portmanteau of two words: sun and seeker. The whole point is to seek the sun. For somebody who can't stand sunlight this, obviously, isn't an appealing prospect; so, from Caliban's point of view, the "keyword" (the most important point) is the word "sun". They're literally buying a boat intended to take them somewhere he can't go.

On his deathbed, Xavier again mentions "the Sun Seeker" to subtly reinforce the idea that Seeking the Sun could be some kind of salvation. This pays off in the movie's climax when Caliban, intending to destroy himself rather than continue to betray his friends, throws himself into bright sunlight -- seeking sun -- but instead is unexpectedly transformed into the powerful being of light he was always meant to be (albeit after a painful transition).

The Phoenix-like "Sun Seeker" -- now in his true form -- then provides a way for the x-tots to cross the border over to "asylum" -- what appears to be some dimension- or time- or space-hacking exit to benign-looking, arm-waving aliens beckoning the kids to Deep Space Nine or Yoda's Hut or the Weinstein Company's daycare nursery. Thank god -- we're so tired of laser beams rising into space!

Right? Because we all recognized, halfway through the movie, that the "border" couldn't be a literal national border, and the "asylum" wasn't merely a political one... Because big pharma's ruthless mercenaries won't care about borders... Right? (Especially Canadian ones!)

Or should I have stayed for the end?