Certainly looks a little like driftwood, particularly the wide end. However there are indications that it could be Ambergris. I would really need to see some better pictures of it. We have acquired lots of mature Ambergris and have seen pieces that resemble that photographed. Higher definition pictures would help, especially ones looking at its cross section.
ps I would recommend that anyone who has an interest in anything and everything you need to know about Ambergris, should buy Chris Kemps book "floating gold" it gives a great insight into the subject
The definitive test is the hot needle test, but only when you are familiar with the scent that emanates... there are a huge range of items that will float, will give off smoke to a hot needle test and which will leave a dark tarry pool afterwards. Even the aforementioned stinking dark pieces will still exhibit the amber note in the mix of the "Oily / fishy" and dungy notes which can really be overpowering in those fresh pieces. There are a couple of youtube clips online that give a lot of visual information... the visual being only half the battle though... look up "potvis schat" on youtube and you'll get the others clips from there. Chris Kemps book is well worth the read and for reference /guidance... And no, I'm not Chris Kemp! in disguise!!!!