When I had my 2008 Shamrock 183 Hybrid the fresh water tank was under a dinette seat and above the camper frame. The drain was accessed under the seat (push/pull arrangement), not under the camper itself. Maybe yours is like that???
2015 Shamrock 231KSS, Oyster shell
2016 Chev Silverado LT Z71 Ext. Cab, 4x4, 5.3L V/8
Reese Straight Line WDH, 2000W Honda Gen.
2 Old Town kayaks & 2 Boston Terriers - Zoey/Gonzo
Lar & Ruth
55 nights camping in 2015, 45 in 2016