Bosses

There are currently 4 bosses in sandulator:

Omega Sea Bass
The Omega Sea bass can be found right next to the mountain on the beach island, in the very back left corner. The fight starts as soon as you drop into the arena. No items are required for the fight. As a reward, you get the "Gills of Glory" buff, which gives you +2 max oxygen, up to +4 if you fight it again. You also get the "defeat the omega sea bass" badge.

Mr Coolbot
Mr Coolbot can be found on a snowy island past the icebergs near the Main Island. A depth buster is required to enter the arena. They can be bought at Walmar Settlement on Iceland, or created on the beach island. As a reward, you get the "Toxin Reducer" buff which, as you can assume, reduces toxins. This can be upgraded by fighting Mr Coolbot again. You also get the "defeat mr coolbot" badge.

Obama
Obama can be found in the corner of the map between the swamp islands and the trash island, right behind the S.S. And. No items are required for the fight, but an aerogel bucket may be useful for dodging attacks. As a reward, you get the obamium, which increases health regen. It cannot be upgraded. You also get the "obamium" badge.

Sand God
Sand God can be found below Ganter's house, which can be accessed after completing the quest Ganter's Sandcastle. A telekill bucket, blood, brazilium/Somebody's remains, and possibly toxin reducing items such as a sponge are required for fighting the Sand God. A full walkthrough of how to get to the fight can be found on the Sand God's page. As a reward, you get a piece of God Sand, which sells for a large amount of money. You also get the "no more sand lord" badge.