1) if you play underworld helmsman, best is to play Samurai Spirit or more Deadly Nightmare. reason being, u call him out max only 2x.. and he is special summon to be replaced by a better rear guard. his boost is useless..
2) Grade 1 Ghost pirate, i suggest u put 2 or remove all.. i understand that u r trying to rush your opponent down w it by discarding 1 card. but his effect is only for attacking n not boosting. so if i were u, i would replace em w samurai spirit.
important thing is, regarding the other clans, they can "fire" off ur grade 1 just by CB-ing.. so its best u use some G1 which can be summon back on.
or if you r discarding cards in order to special summon them up the next turn, make sure you have enough dmg to last till ur grade 3.. since u r playing 2 Death seeker.
3) sea Navigator, silver is a G2 w 8000 atk power. its not he is useless, but 8k atk is kinda small now, you cant hit through any common rear guard or vanguard w it. n if you do, ur opponent most likely on needs to block it w 10k or 5k guard. its having a draw effect, so ur opponent definetly wont let it go through.
you might wan to change Blue Blood back.
if you r playing Sea navigator, why r u playing ghost pirate of the freezing night? its contradicting your entire deck.. more hand size, unable to get boost bt 3k..
i suggest you play 4 blue blood n the chef which can unflip dmg. Unflipping dmg will help u when u reach G3. etc, Thanatos, Ice prison
4)too much G3 (8 shd be enough), u shld remove Night storm, play more deadly swordmaster. its 11k atk power. its time to abuse GRANDBLUE G3..
if you r playing 3 Basskirk, that means you have to keep calling either deadly nightmare or deadly spirit back to the field. in just a turn, u r only able to that twce. as it requires to SB 4 in order to call back ur 2 units.
so far this is how i see your deck..
just my suggestion n opinion~