But don't let a gentle bump on the sea put you off trying over rough ground marks. Rough seas and spinning are not a good marriage. Your problem stems from a mixture of things. Firstly, pick either a stainless steel French boom of between 12 and 14ins long, or the Mustad KF Tubi boom in the 300mm length. Booms of this length keep the trace away from the main line on the descent.
Shorter ones cause constant problems.
When you're ready to start fishing don't just drop the eel and lead over the side and start the descent. Hold the eel in your hand until the lead weight is touching the seas surface, but with the reel still in gear. Now throw the redgill into the tide and allow the trace to fully straighten out with the flow. When this is achieved you can flick the reel in to free spool and begin the descent to the bottom. Don't let the lead fall freely as this will increase your chances of a tangle.