Tommy. Have the batteries been charged up? Are you using rechargeables or ordinary batteries in the transmitter? were there other boaters on the pond with ordinary boats and radio control gear?
Unplug and re-plug all the connections. Oddly enough another chap on our pond a week or so ago had a similar problem…boat would not run IN the water but ran ok out….it also appeared to be ok(ish) if he revved it up and THEN put it in the water….most odd..BUT have not seen him since to see if he got to the bottom of it. He was muttering about motor timings on the brushless ESc, but your RTR would not have any adjustment in this regard.
Ashley (keep the receipt safe)