舰艇 is a general term for warships and naval vessels of various sizes. It is more formal than 船 (boat/ship) and is specifically associated with military use.
港口里停着好几艘大型舰艇。
gǎngkǒu lǐ tíng zhe hǎo jǐ sōu dàxíng jiàntǐng.
Several large warships are docked in the harbor.
这艘舰艇配备了最先进的武器系统。
zhè sōu jiàntǐng pèibèi le zuì xiānjìn de wǔqì xìtǒng.
This warship is equipped with the most advanced weapons systems.
海军舰艇在附近海域进行了演习。
hǎijūn jiàntǐng zài fùjìn hǎiyù jìnxíng le yǎnxí.
Naval vessels conducted exercises in the nearby waters.