Good manufacturers/makes
Wilderness Systems – Tarpon 100/120
Emotion Temptation (10 or 11)
Perception Scooter (comfort)
Ocean Kayaks Frenzy
These are Sit On Tops and would be ideal for starting off as you don’t need to learn to roll, they are generally quite stable, they don’t fill up with water if you capsize and they are easy to get back into if you do come out. You will get wetter and colder than a sit-in.
Sit In Kayaks are more advanced – manufacturers/models:
Dagger Blackwater or Approach
Robson Waikiki
You won’t go far wrong with any of the above manufacturers. Avoid cheap Chinese imports. A lot of sit on tops are fun beach boats which are more suited to surf than rivers/estuaries and coastal waters.
Obviously this is all very simplistic but hope it helps.
Rich.