These free printable under the sea 3rd grade spelling worksheets give you a full week of simple, ready-to-use spelling activities.
They are part of a full 3rd grade homeschool curriculum built around weekly themes, with each week designed to keep learning feeling fresh and engaging.
These worksheets will help kids learn to spell the math-themed spelling list for this week of 3rd grade spelling words.
Skills covered include:
- spelling and vocabulary practice
- rhyming words
- verb tenses (-ed and -ing)
- synonyms and antonyms
- alphabetical order
- plural nouns
- missing vowels

If you’re looking for no-prep spelling practice that still feels a bit fun and different, this ocean-themed set is easy to use at home or in the classroom.
If you’d like to see how these worksheets fit into a full week of learning, including the day-by-day plan, you can view the complete under the sea 3rd grade plan here.
The answer keys are included at the bottom of this post.
Difficulty Level
These worksheets are designed for 3rd grade students.
They give kids practice with 3rd grade spelling words while also working on language arts and grammar skills.
Some activities may require a quick explanation or refresher, but everything is laid out to keep it simple for parents. The activities are short and varied to help keep kids focused and avoid boredom.
Missing Math Words Worksheet
This first worksheet introduces the spelling words for the week.
It also works as an under the sea themed reading, spelling, and vocabulary activity. Students read each sentence and fill in the missing word using context clues.
The words include math vocabulary like length, width, perimeter, and area.

The sentences also include some higher-level ocean vocabulary to help build word knowledge. Words like lagoon, blubber, marine biologist, and anemone are included. You may want to look these up together if they are unfamiliar.
Rhyming Words, Verb Tenses, and ABC Order
This worksheet gives students a mix of word work activities in one page.

It’s designed to keep things from feeling repetitive while still reinforcing important spelling and grammar skills.
Vowels, Synonyms, Antonyms, and Plural Nouns
This worksheet focuses on reinforcing spelling while adding in grammar practice.
Filling in the missing vowels helps students think carefully about how words are built, and the other activities give them more practice using those same words correctly.

Download and Print
You can download these free printable 3rd grade spelling worksheets using either form below.
The PDF will open right away, and a copy will also be sent to your inbox.
These worksheets print in black and white to keep ink use low. Print pages 1-3 to only print the worksheets.
You can find the answer keys below.
More Under the Sea Activities
To go along with this under the sea theme, kids could try:
- this how to draw a shark activity
Answer Keys
The answer keys for these spelling worksheets are below.
Page 1 – Catch the Missing Math Words Answers

Page 2 – Rhyming Treasures in Shells Answers

Page 2 – Bubble Up Your Verbs Answers

Page 2 – Swim Into ABC Order Answers

Page 3 – Fin-Tastic Vowels Answers

Page 3 – Hook a Synonym Answers

Page 3 – Crab the Opposites Answers

Page 3 – Dive Into Plurals Answers

