I took my first pool class recently on my way to OW certification and had a few issues. Before class I was gifted from a friend a brand new, never used but still 18 year old MARES Quatro Fins. I bought 5mm booties to wear with them as well. So the issue was when I was in water when ever I would go to my knees I kept lurching forward and felt like my feet wanted to float up behind me. Also when ever I tried to Trim Out my feet would rise up and Id go ass over head. Is this a fin issue or just be not being adept as using my BCD? I could stand like a statue on bottom no problem but I couldn't kneel or hover seated to save my life. I ask about BCD because when I would do small puffs Id go from nothing to all of a sudden shooting up like a rocket...with little transition in between. Any recommendations appreciated...Thanks.