installing a small hatch on a Ocean Kayak

I wanted to add a small plastic hatch cover to my kayak and wasn't sure what type of sealant I should be using. The hatch will be towards the center cockpit   Thank you Robert

Marine GOOP.

https://www.amazon.com/Amazing-GOOP-170011-Marine-Adhesive/dp/B000BQUI7S

Another vote for goop. And if you want to put a hatch someplace that is not flat, you can cut a ring out if plastic (starboard is the best brand) and easily shape it with a rasp.

Another vote fior goop. And if you want to put a hatch someplace that is not flat, you can cut a ring out if plastic (starboard is the best brand) and easily shape it with a rasp.

Starboard makes a great backer for the hatch ring, too.  I've also used the Seaboard brand of HDPE as backer board when I couldn't find thin Starboard...

Starboard: https://www.amazon.com/WHITE-KING-STARBOARD-12/dp/B00S1KSH3S/ref=sr_1_4?s=industrial&ie=UTF8&qid=1494415851&sr=1-4&keywords=starboard+white

Seaboard: https://www.amazon.com/Seaboard-Density-Polyethylene-Finish-Length/dp/B00JPHB4EK/ref=sr_1_14?s=industrial&ie=UTF8&qid=1494415500&sr=1-14&keywords=Seaboard+High+Density+Polyethylene+Sheet

Btw, you can often find fairly large pieces of starboard for cheap in the scrap bin at Tap Plastic.

Thanks guys I will be placing a Amazon order today, I love starboard material    Thanks again  Robert