How to start a ml320 1998 that won't?

i just received my 1998 ML320 from florida,the car wouldn't start since it got of the boat,i thought it was gas since they always take out the gas for safety so i put 5 gal in it,when i start the vehicle it just starts and then shuts off instantly,i've checked the fuel pump seems to work,fuses ok,need help,since it came from a two day trip on sea,friends say it might be moisture in the air flow meter,i even spray a little bit of carb cleaner in the intake hose while trying to start and it seems that it wanted to start but instead of shutting down instantly,it waited about 2 sec.