what is the true statement about immersion suit ?

First of all, the correct statement is that a immersion suit must be able to turn an unconscious person's mouth out of the water within 5 seconds, without any assistance.

Why other typical options are FALSE

❌ The immerison suit is flameproof and provides protection while swimming through burning oil.

Immersion suit is flame-retardant (2-second fire resistance), NOT flameproof. Cannot survive prolonged swimming in burning oil.

❌ Immersion suit can provide a protection against hypothermia indefinitely / for weeks.

Only extends survival time, cannot prevent hypothermia forever.

❌ Immersion suit storage container may be locked.

Stowage boxes must NOT be locked for instant emergency access.

❌ It can withstand exposure to gasoline/mineral spirits and remain serviceable.

Fuels will damage suit material.

❌ You must wear an additional lifejacket over immersion suit.

SOLAS approved immersion suit has inherent buoyancy; extra lifejacket is not required.

❌ A small puncture will not reduce its performance.

Water ingress through holes ruins thermal insulation.

More detailed rules (LSA Rules/Chapter 3 of the SOLAS Convention) are available for your reference:

Can be deployed and donned without assistance within 2 minutes.

The wearer can jump into water from a height of 4.5 meters without taking in water.

Covers the entire body except the face.

Equipped with a whistle, reflective strips, and personal lighting.

Permitted activities: walking, climbing ladders (before disposal).

Will not continue to burn or melt after being completely engulfed in flames for 2 seconds.