Ok, so the first one is really simple so I'm not going to go in too much detail with this one. You just need to kill 100 fish, most people unlock this costume around L1 3-2.

Some tips to help you achieve this costume:

• The trinkets that i prefer for this achievement are: Venuz's Blessing+Granola Bar+Hot Sauce+(Plastic Straw or Plastic Fangs or Romantic Novel)

• You should use the stock weapon (even though the unlockables look way cooler because unlockables are very situational), the pistol deal more damages than an AK per shot and it's more accurate, also with the Venuz's Blessing you can one-shot kill the fish

• For this character you should build as many rafts as you can by holding down the right mouse button ( Don't kill all of the critter that come at you, save one so the game doesn't advance right away so you have more time to fix up your broken raft)

For the second character costume you will need to kill 80 sharks in a single run and most people unlock the skin ,you will unlock this achievement around late L2 to early L3.

Some tips to help you :

• The trinkets that I recommended for Chauncy's second costume are : Venuz's Blessing+Hot Sauce+Granola Bar+(Plastic Fangs,Romantic Novel,Dead Fish)

• For the weapon I once again recommend you going with stock and not the unlockable (because stock are more consistent) you will be able to kill most critters with one shot without the need of Venuz's Blessing. If you have the Hot Sauce trinket and every pellet connected you basically can get double damage every single shot, (every time your gun shoot out 7 pellets with the Venuz's Blessing it double to 14 pellets.)

• You should also save a slow moving critter like a Fish to rebuilt your raft every round
  • For the rafting technic: I like to build a small box surrounding a body of water almost like those Asian fish farms on the sea. For this building technic you can go from point A to point B faster then walking on raft, but be worried for those floating rocks they can seriously wreck your raft to dust.(For example https://steamuserimages-a.akamaihd.net/ugc/1724297781938016657/5E86AA01C979DDA7ED5431E72630E0BDC6E44BB0/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false
    or like this https://steamuserimages-a.akamaihd.net/ugc/1724297781938117590/AF6F9DAB66C20A70644FC71AF796906CA0BB37F1/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false )
  
  You might think that this rafting technic build too many small box why don't i just build a really big box. Well then your eyes are bigger than your stomach my friend, if you built it to big then you will be in the water for way longer (more time in the water mean less time shooting) and of course the other sharks they will ramp into your raft faster than you can react especially in the late game so keep it small simple and split them into small part so you can get out of the water any time you wanted
  (Fpr example don't built it like this https://steamuserimages-a.akamaihd.net/ugc/1724297781938119100/55101388D3E89CD60DDC18AA4337325C07FF7D80/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false )
  

To get Roboto's second costume you need to complete L3

Again here are some tips:

• Yet I advice you once more time to use the stock minigun for it's the most reliable source of damage and it's the easiest weapon to use, the lazer rifle can be really powerful if you can aim all of your shot (but if you miss one shot on L2-L3 it's going to be an end to your run) so i highly recommend using the minigun, unless you have a very very sharp aim .

• So for the minigun build that I like the most are: Venuz's Blessing+Granola Bar+Hot Sauce+(Romantic Novel+Plastic Fangs+Plastic Straw)

• With this minigun build, in the late game (L2-L3) you can basically shoot infinitely bullet because of the sheer amount of critters can cover your whole screen. (With the Granola Bar trinket, your weapon's reload meter will be instantly filled a little bit upon killing an enemy. Every click you shoot out 2 bullets so with the Venuz's Blessing you shoot out 4 bullets per click so this baby can shoot out 240rpm, with the Hot Sauce trinket you can only imagine the amount of double damage bullet. You will need 3/4 of the weapon's reload meter to kill a tentacle of the Kraken that mean that you will need to reload 4,5 time to kill the Kraken. You should also shoot in burst and only use full auto when there are too many critters because this gun run out of ammo quick like really quick).

• For the lazer rifle build the trinkets that i use are : Venuz's Blessing+Granola Bar+Plastic Straw +(Romantic Novel+Plastic Fangs+Hot Sauce) just don't miss a shot and you will be fine.

• With the raft technic: I like to build little squares (8 blocks of rafts surrounding a 1 block of water in the middle) because Roboto can shoot when he is hovering on the water, also it is very hard to drown if you keep on moving because you will need to stand directly on the square of water to start the hovering sequence (most of the time you won't stand directly on the square of water) but your worst enemy are shark remember with this raft technic you are sacrificing defense for mobility so kill the shark first if you can.
  Here is a picture for reference: https://steamuserimages-a.akamaihd.net/ugc/1724297781938221290/ECA9B43F91959551CF1152D595D6845E79035469/?imw=256&&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

Ok in this section I'm going to tell you some little tips that i found out while playing the game :

• Build infinite rafts : If you save the green ghost pirate for last and don't kill him then the game won't advance until you kill the last critter. So what you can do is build a lot of rafts in this time to prepare yourself for the next level (he shoot every 3 seconds or so), I also use this trick with the fish when getting the second costume for Chauncy because it moves slowly underwater so i can outrun him underwater with Chauncy

• Getting Plastic Straw without needing the trinket: If you need the trinket but you don't have it then lowering your fps to about 50-40 fps should do the trick (lowering it to 30 fps is super slow like you can see ever bullet shoot out of the minigun )

• Getting Plastic Fangs without needing the trinket : The healing mechanic in this game is that if you get hurt they will start giving you hearts to heal up so if you get hurt for half a heart and doesn't heal up they will keep giving you more and more heart (once time i saved up to 8 hearts on a raft trip). This is based a lot on luck so if you're unlucky don't use this tip. The greatest downfall of this is that i got too greedy and doesn't it the heart because i want more hearts so i die. (you can hurt your self for half a heart by getting hit by a rock or a shark,ect )

• If are on L2 1-1 and you collect the egg and then finish the going through the ice level you will get to choose another trinket meaning that you will have more then 4 trinkets but the ice level can be very difficult so be careful.

Here is the final tip: open your favorite song and play the game, good luck on getting them achievement you are going to need it.

P/S: If you have any question leave them down in the comment and I will do my best to respond to your question