possible short?

[lampen]

so here is the background on this, that way you can see the whole picture. my last couple of outings my batter has slowly been weaker. so i figured it was time to replace, but i had some new battery acid, so i tried refreshing it. i charged the batter up, and tested it, and it seemed to hold a charge even under load. so i put the newly refreshed battery in my seadoo, and it cranked right over, but didn't start cause it has sat for a few weeks. i went to crank it over and it was as if the battery was very weak. i took it out and tested it, and it was almost dead just like i expected. thinking the battery was just to far gone, i opted to borrow a brand new battery from my friend. tested it, everything tested fine, held a charge and so on. installed the battery, and the same thing happened. cranked right over, but next time, battery was very weak. so this brings me to thinking there might be a short, but i'm not sure where it would have developed, because i haven't messed with anything electrical. if anyone knows of what to look for, has any idea of what it could be, maybe something i'm overlooking or not thinking about, please, let me know. i need to get out to the lake soon!