Assassin X Assassin

Witch!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Now IMA have to change the ending Before only three would survive and graduate.

Predictable; it makes sense with an assassin school that only the best would survive - an assassin's job is dangerous, so there's no point in letting the weak survive it. There's nothing wrong with predictable, providing you can make it epic and throw in a couple of plot twists elsewhere.

Personally the point is an important part in the story. It's a great opportunity to get the ball rolling plot wise. The main character has weapons, but what sets him apart? I think it should be what doesn't set him apart that will actually make the story compelling. So I'd make the boat be a 10+ chapter arc where you introduce a few types of characters. I'd introduce two characters to be friends at the same time. One will actually be using the main to get ahead and the other is just a straight up nice guy. Use these three to create tension. Alongside this should be an overall genius. This character can be the rival but not sauske type more like akira from Hikaru No Go. Each character should have excellent and interesting skills, let's say the genius uses pinpoint precision assassinations using only needles which is why he is so impressive. Maybe the best friend is an excellent shot which can compliment a vengeance induced main character who relies mostly on hand to hand but has difficulty bringing himself to kill. I'd definitely draw a series like that.

Forgot the most important part. Use the boat as a preliminary tournament and have people fight. Let's say only 10 kids get to enter. The rest die. Bam. Tension

I was going to do some of does thinks but thanks for some good advise I'll think I'll hold the boat in tell at least like chapter 6

Than what's the point in the school if they almost all die on the boat I was thinking that he could meet new friends/enemies and scope out the skill and fame of some of the other students.I also thought that he could learn some basic info about the school.

Well the first chapter of a story manga is usually 60 pages. It'll take your entire first chapter to get people to care about your main character in most cases. However doing lots of scoping and such is illogical. He's new, he doesn't know shit, and you should really stress that. Use other characters to get his ball rolling, and don't add too many. Let's compare to arguably similar mangas. "One Punch Man" and "My Hero Academia" my hero has alot of characters in the beginning, too many in fact it gets you lost pretty fast, and unless it was for chapter 0 I'd probably not care about the main character. One punch man is much more well paced about this. Moreover the point is (in killing everyone)itd be a school for the eelite you'd have only 30 kids in the whole school. Enough to all have them be main characters eventually. Thematically itll also increase the isolation of the main character. This is no place to screw around there's only 30 kids at this school and all of them could kill you easily. Too many kids is actually less scary as many of them would be small fry. Set up the fear isolation and brutality level early on.