How dangerous is a wet server room floor

Carpet is a big 'NO! NO!!' for a room hosting equipments that are of high value, because of the fire risk. Water is too, for obvious reasons. You should straight call maintenance immediately and have them repair the drainage system. The water could really cause problems, inform your superiors right away and draw their attention on the matter.

Nobody has mentioned "why" water in a server room is dangerous. It might be obvious, but just to put it out there...

Server rooms have a good deal of electrical equipment running on AC and DC current. Usually they are well grounded, but sometimes insulation breaks down, or a wire gets pinched. A person touching an electrical potential is protected by their skin or clothing (gloves). This provides a resistance that prevents a current running from the higher potential piece of equipment to ground. Adding water to this situation decreases the resistance allowing more current to pass through the body. (in both the AC and DC forms of Ohms law Current = Voltage / Resistance(Impedance))

If you are wet, a 60V potential difference can send enough current across your heart to kill you. Not 120V, not 240V, 60V. You don't need a main electrical cord to cause the short.

To keep beating the horse... You are likely legally permitted to refuse to enter the server room. In the United States, OSHA and the DOL regulations may apply to this situation. OSHA standard 1910.22(a)(2) is what you can reference. Not that it is a good idea to throw around OSHA regs, but they exist for a reason.

If you do need to work in that environment, then invest in some good PPE (gloves, shirt and shoes) to afford yourself some protection. But seriously, this is a bad situation and should be fixed.