Your dealer should pressure and vacuum check the gearcase to find out how the water got in. Running in the shallows and picking up sand or mud can wear the driveshaft seals fairly quickly. Having fishing line wrapped around the propshaft can damage those shaft seals. If the leak if from the same 2 seals and there is no sign of wear or damage, then perhaps the housing holding them is faulty.
Your dealer has to examine and determine what happened first, then can correct it.
"There is never just one thing wrong with a boat";
-- Travis McGee, main character in a book series by John D. McDonald
The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.
The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.