Sea Fishing is without a doubt the hardest fishing technique to master, on a boat or on the beach each has its on challenges and both are incredibly hard I would know from personal experience. On a boat their a tricky tides and tricky fish to deal with, perhaps the Sharks or Marlins are your targets, maybe smaller faster game fish either way catching a a fish at sea on rod and reel is difficult. When fishing from land to sea everything has to be right, the weather, the timing, the fish. Beach fishing is a long process and a game of patience think carp fishing for sharks. Setting a rod is an easy task but waiting for the fish to come closer to shore to catch it and even then they won't bite or choose not too.
You can also do kayak fishing which I would not recommend because personal I can't swim so I wouldn't want to be capsized but kayak may be the most dangerous fishing of them all, you don't know who will bite or how far they'll take you out.